Ultrasound garment

ABSTRACT

Disclosed is an ultrasound assembly. The ultrasound assembly includes a garment configured to be affixed to a portion of a living body, and at least one ultrasound transducer having a fixed position on the garment and configured to provide at least one of: produce and receive, ultrasound signals that pass through the living body. The ultrasound assembly further includes an ultrasound processing unit operatively associated with the at least one ultrasound transducer and configured to process the ultrasound signals following passage through the living body, and an ultrasound operator-interface unit operatively associated with the ultrasound processing unit and configured to provide information with respect to the ultrasound signals following passage through the living body.

RELATED APPLICATION

This application claims priority from U.S. Patent Application Ser. No.61/056,069 filed 27 May 2008, the content of which is herebyincorporated by reference as if fully set forth herein.

FIELD AND BACKGROUND OF THE INVENTION

The present invention, in some embodiments thereof, relates to fixingthe position of an ultrasound transducer with respect to a subject and,more particularly, but not exclusively, to fixing the position of anultrasound transducer within a garment affixed to the subject.

Ultrasound is a well matured medical imaging modality. It providestwo-dimensional (2D) and/or three-dimensional (3D) anatomic informationas well as a plurality of physiological and functional parameters atrelatively high refresh rates, reaching an order of 100 frames persecond for 2D imaging.

The imaging platforms are portable and reasonably priced. However,ultrasound imaging suffers from some disadvantages, chief of which arelow image quality compared to other imaging modalities, for exampleComputed Tomography (CT) and Magnetic Resonance Imaging (MRI); andlimited volume coverage.

Conventional phased array transducers have a limited field of view dueto limitations at the beam steering end, i.e., due to off-broadside beamwidening; the effective area of planar transducers decreases with theoff-broadside angle, thus increasing the beam width.

The maximal beam penetration depth is also limited by signal attenuationwithin the tissue. Decreasing the transmission frequency reduces theattenuation and increases the penetration depth, but also worsens thespatial resolution.

One of the methods known in the art for addressing these issues is imageregistration and compounding. The term ‘registration’ relates to theprocess of finding a transformation that maps each point in one image orcoordinate system to corresponding points in another image or coordinatesystem. The term ‘compounding’ relates to the combination of data frommultiple registered images to produce one or more registered images.

The registration process may either be algorithm based, or sensor based.

In algorithm based registration, the sole input is a set ofreconstructed imaging planes or volumes. For example as described byForoughi P, Abolmaesumi P, Hashtrudi-Zaad K; “Intra-Subject ElasticRegistration of 3D Ultrasound Images”; Medical Image Analysis 2006;10:713-725.

In sensor based registration, data acquired by positioning and/ororientating sensors is also utilized. For example as taught in US PatentApplication 2007/0081709; Apr. 12, 2007 by Warmath R J, Herline A J;“Method and Apparatus for Standardizing Ultrasonography Training UsingImage to Physical Space Registration of Tomographic Volumes from TrackedUltrasound”.

The documented advantages and features of ultrasound image registrationand compounding include, for instance:

-   -   i. Field of view extension; for example as described by Poon T        C, Rohling R N; “Three-Dimensional Extended Field-Of-View        Ultrasound”; Ultrasound in Medicine and Biology 2006;        32:357-369.    -   ii. Freehand three-dimensional (3D) imaging, i.e., generation of        3D images using a manually moved 2D imaging probe; for example        as described by Treece G M, Gee A H, Prager R W; “RF and        Amplitude-Based Probe Pressure Correction for 3D Ultrasound”;        Ultrasound in Medicine and Biology 2005; 31:493-503.    -   iii. Speckle noise reduction. Speckle is a result of the fact        that the reflecting particles within tissues are much smaller        than the wavelength used. The effect of speckle may be modeled        as multiplicative noise. Speckle patterns are very sensitive to        small changes in the relative location of the transducer and the        tissue volume, and can be reduced by local averaging over        several frames, taken at different times or probe        positions/orientations. For example as described by Krücker J F,        Meyer C R, LeCarpentier G L, Fowlkes J B, Carson P L; “3D        Spatial Compounding of Ultrasound Images Using Image-Based        Nonrigid Registration”; Ultrasound in Medicine and Biology 2000;        26:1475-1488.    -   iv. Minimization of shadowing artifacts. Shadowing is caused by        tissues along the ultrasonic beam that have a high reflection        and/or attenuation coefficient, so that the ultrasound energy        reaching tissues further away from the transducer (along the        ultrasonic beam) is significantly reduced. This differently        affects ultrasound images acquired from different angles, and        can therefore be mitigated by spatial compounding. For example,        as described by Krücker J F, Meyer C R, LeCarpentier G L,        Fowlkes J B, Carson P L; “3D Spatial Compounding Of Ultrasound        Images Using Image-Based Nonrigid Registration”; Ultrasound in        Medicine and Biology 2000; 26:1475-1488.    -   v. Spatial resolution enhancement, using datasets obtained at        multiple spatial locations and/or orientations of the probe; for        example as described by Yang Z, Tuthill T A, Raunig D L, Fox M        D, Analoui M; “Pixel Compounding: Resolution-Enhanced Ultrasound        Imaging for Quantitative Analysis”; Ultrasound in Medicine and        Biology 2007; 33:1309-1319.    -   vi. Estimation of speed of sound factors within different        tissues, using time delays measured at different directions; for        example as taught in US Patent Application 2007/0167757; Jul.        19, 2007; Haimerl M; “Determining Speed-of-Sound Factors in        Ultrasound Images of a Body”.    -   vii. Change estimation and regional motion evaluation, utilizing        2D or 3D imaging information acquired for the same tissue volume        at several timeframes. In some cases, the registration may be        performed globally, but local registration is usually required,        tracking the location change over time for every small region,        for example as described by optic-flow techniques. If the time        difference between consecutive images is relatively short,        applying cross-correlation functions to the local speckle        pattern can allow accurate regional motion assessment. For        example as taught in U.S. Pat. No. 5,876,342; Mar. 2, 1999; Chen        J F, Weng L; “System and Method for 3-D Ultrasound Imaging and        Motion Estimation”.    -   viii. Angle independent Doppler measurement. Standard ultrasound        systems estimate flow velocity, for example blood flow velocity,        using the Doppler Effect, which only provides information        regarding the radial component of the velocity vector. When        multiple receiving transducers are employed, placed at different        angular locations with respect to the target volume, one can        estimate the magnitude and orientation of the flow velocity        vector. For example as taught in U.S. Pat. No. 5,409,010; Apr.        25, 1995; Beach K, Overbeck J; “Vector Doppler Medical Devices        For Blood Velocity Studies”.    -   ix. Intra-operative guidance, by registration of intra-operative        ultrasound images to images acquired beforehand by any modality;        for example as described by Barratt D C, Penney G P, Chan CSK et        al.; “Self-Calibrating 3D-Ultrasound-Based Bone Registration for        Minimally Invasive Orthopedic Surgery”; IEEE Transactions on        Medical Imaging 2006; 25:312-323.

Some state-of-the-art 3D imaging probes with improved field of view havealso been suggested, for instance:

-   -   i. As taught in International Patent Application WO2004/001447;        Dec. 31, 2003; Poland and Sumanaweera et al.; “System and Method        for Electronically Altering Ultrasound Scan Line Origin for a        Three-Dimensional Ultrasound System”; and as taught in US Patent        Application 2006/0078196; Apr. 13, 2006; Sumanaweera T S, Cai A        H, Ustuner K F; “Distributed Apexes for 3-D Ultrasound Scan        Geometry”; which describe 2D or multi-dimensional (MD) phased        arrays which can adaptively generate scan lines apparently        emanating from a location (“apex”) other than the geometric        center of the transducer probe. Multiple apexes may be        generated, allowing the optimization of the scanned volume to        the transducer's characteristics.    -   ii. As taught in US Patent Application 2006/0173333; Aug. 3,        2006; Sudol W.; “Two-Dimensional Transducer Arrays for Improved        Field of View”; where a similar concept is presented, wherein        different groups of adjacent rows and/or columns of transmitting        and/or receiving transducer components are activated at        different times. Sudol also suggests the possibility of using a        convex 2D array, as well as using two or more probes        concurrently.    -   iii. As taught in US Patent Application 2007/0066902; Mar. 22,        2007; Wilser and Mohr; “Expandable Ultrasound Transducer Array”;        describing a foldable transducer array, intended to be used        within the subject's body. While folded, the transducer array        has a smaller width or volume, for insertion into and withdrawal        from, for example a hollow region within the subject. When        unfolded, foldable transducer array provides a larger radiation        surface.

Another system and technique, which effectively improves image qualityand increases image volume, is ultrasound computed tomography (UCT). UCTis founded on inverse problem concepts, similar to those used for X-rayCT. UCT has two basic implementations:

-   -   i. Reflection mode: In this case, the source, for example the        transmitting array, and the detector, for example the receiving        array; are on the same side of the subject or the target region.        The transmitting array and the detector are rotated about a        certain rotation axis, and in some cases also translated along        that axis. In each geometric configuration, a short ultrasound        pulse is transmitted, and the reflected echoes, resulting from        discontinuities in the speed of sound within the medium, are        measured as a function of time, which corresponds to the        distance between the reflector and the transducer; for example        as taught in US Patent Application 2006/0106307; May 18, 2006;        Dione D P, Staib L H, Smith W; “Three-Dimensional Ultrasound        Computed Tomography Imaging System”.    -   ii. Transmission mode: In this configuration, the source and the        detector are placed on opposite sides of the subject or the        target region, and are rotated and/or translated together; for        example as taught in U.S. Pat. No. 4,509,368; Apr. 9, 1985;        Whiting J F, Koch R H L; “Ultrasound Tomography”. For each beam,        the time difference between the transmission of the pulse and        its detection on the other side; for example as described by        using rise-time detection or threshold detection on receive;        provides information regarding the overall time of flight, which        is inversely proportional to the average speed of sound along        the beam. The power ratio between the transmitted pulse and the        received pulse provides an estimate of the total signal        attenuation along the beam.

In some cases, multiple sources and/or detectors are used to reduce theoverall scanning time.

Both UCT modes use circular or helical scanning of the subject. Aslightly different geometry has been suggested by Li P C, Huang S W;“Ultrasound Tomography of the Breast Using Linear Arrays”; ICASSP 2005;V-989-V-992; who compressed a female breast between a linear transducerarray and a reflective metal plate. Separate groups of transducercomponents are allocated for signal transmission and reception. Therelative location of the selected groups with respect to the metal platedetermines the path of the ultrasonic beam.

A variation of UCT, called ultrasound diffraction tomography (UDT), isbased on measuring the forward scattered ultrasound field as a functionof cross-range with respect to the incident wave. This technique alsorequires the utilization of more complex reconstruction methods; forexample as described by Louis A K; “Medical Imaging: State of the Artand Future Development”; Inverse Problems 1992; 8:709-738.

Furthermore, ultrasound imaging has the potential to expand its clinicalapplications beyond its presently prevalent capabilities, and alsoprovide tissue classification parameters. Elastography has been proposedas a way to achieve this goal; for example as described by Melodelima D,Bamber J C, Duck F A, Shipleyi J A, Xu L; “Elastography for BreastCancer Diagnosis using Radiation Force: System Development andPerformance Evaluation”; Ultrasound in Medicine and Biology 2006;32:387-396. The term elastography encompasses a variety of techniquesthat can depict a mechanical response or property of tissues. Inultrasound, the elastography premise is built on two known facts:

-   -   i. There are significant differences between mechanical        properties of several tissue components.    -   ii. The time-dependent information contained in the measured        speckle patterns is sufficient to depict these differences        following an external or internal mechanical stimulus. This        stimulus may be generated, for example by applying an external        pressure to the skin surface, or by vibrating a region at a low        frequency.

Ultrasound also has therapeutic applications, using high intensityfocused ultrasound (HIFU) technologies, which increase the localtemperature at a region near the focal point of a high energy ultrasoundtransducer, thus causing local tissue ablation; for example as taught inUS Patent Application 2008/0051656; Feb. 28, 2008; Vaezy S, Chan A N,Fujimoto V Y, Moore D E, Martin R W; “Method for Using High IntensityFocused Ultrasound”.

SUMMARY OF THE INVENTION

According to an aspect of some embodiments of the invention, there isprovided an ultrasound assembly. The ultrasound assembly includes agarment configured to be affixed to a portion of a living body, and atleast one ultrasound transducer having a fixed position on the garmentand configured to provide at least one of: produce and receiveultrasound signals that pass through the living body. The ultrasoundassembly further includes an ultrasound processing unit operativelyassociated with the at least one ultrasound transducer and configured toprocess the ultrasound signals following passage through the livingbody, and an ultrasound operator-interface unit operatively associatedwith the ultrasound processing unit and configured to provideinformation with respect to the ultrasound signals following passagethrough the living body.

In some embodiments of the invention, the garment is configured to coverat least a portion of a body part of the living body including at leastone of: an abdomen, a torso, a pelvis, an arm, a foot, and a head.

In some embodiments of the invention, the garment comprises at least oneapparel including at least one of: a belt, a shirt, and a pair of pants.

In some embodiments of the invention, the garment is comprised of atleast two parts, separated by at least one band, the at least one bandbeing at least one of: relatively stretchable, and relativelyunstretchable.

In some embodiments of the invention, the garment has an openconfiguration which may be adjustably closed around at least a portionof a body part and includes a closure including at least one of: Velcro,straps, tape, and clips.

In some embodiments of the invention, the garment includes an innersurface and an outer surface and includes, to keep the garment in place,at least one of: sticky patches on the inner surface, vacuum chambers onthe inner surface, and pressure chambers on the outer surface.

In some embodiments of the invention, the garment includes at least onefixation point to which the at least one transducer removably attaches.

In some embodiments of the invention, the garment is configured toreceive at least one mechanical fixture operatively associated with theat least one transducer, the mechanical fixture configured to maintainthe at least one transducer affixed to the garment.

In some embodiments of the invention, the at least one transducercomprises at least one transducer array.

In some embodiments of the invention, the at least one transducer arraycomprises a plurality of transducer arrays.

In some embodiments of the invention, the plurality of transducer arraysare spaced with respect to each other according to at least one of: adistance, and in close proximity.

In some embodiments of the invention, the at least one transducer arrayis configured in at least one of: a one-dimensional array (1D), a twodimensional array (2D), and a multi-dimensional (MD) grid pattern.

In some embodiments of the invention, the at least one transducer arraycomprises a grid pattern including at least one of: Cartesian andhexagonal patterns.

In some embodiments of the invention, the at least one transducer arraycomprises a sparse grid.

In some embodiments of the invention, the at least one transducer arrayincludes at least one sub-array.

In some embodiments of the invention, the assembly includes anultrasound beam-forming unit configured to produce ultrasound beampropagation wherein at least one of: at least one sub-array, the atleast one array, a plurality of transducer arrays, and the at least onetransducer are configured to provide beams consisting of at least oneof: transmitting, and receiving, and the ultrasound processing unitincludes a software module configured to process information from theprovided beams.

In some embodiments of the invention, the ultrasound beam-forming unitis configured to produce ultrasound beam propagation in at least one of:two-way, and one-way, through the living body.

In some embodiments of the invention, the at least one transducer arrayincludes at least one acoustic lens covering at least a portion of oneof: at least one sub-array, the at least one array, a plurality oftransducer arrays, and the at least one transducer.

In some embodiments of the invention, at least one of: at least onesub-array, the at least one array, a plurality of transducer arrays, andthe at least one transducer, are configured to scan at least one of: asurface, and a volume.

In some embodiments of the invention, at least one of: at least onesub-array, the at least one array, a plurality of transducer arrays, andthe at least one transducer, are configured to scan using at least oneof: electronic scanning, and mechanical scanning.

In some embodiments of the invention, the mechanical scanning isperformed by at least one of: swinging, rotating, and oscillating.

In some embodiments of the invention, the assembly includes at least onerail juxtaposed along the garment and at least one of: at least onesub-array, the at least one array, a plurality of transducer arrays, andthe at least one transducer, are configured to move along the at leastone rail.

In some embodiments of the invention, the movement is induced by atleast one movement of: manual, and motorized.

In some embodiments of the invention, the at least one rail includescogs operatively associated with at least one motor having at least onecog wheel configured to cause the movement along the at least one rail.

In some embodiments of the invention, the assembly includes at least onetransducer-locating sensor operatively associated with the ultrasoundprocessing unit, the at least one transducer-locating sensor occupyingat least one position of: on the garment, and at a distance from thegarment, and the ultrasound processing unit includes a software moduleconfigured to process spatial information from the at least onetransducer-locating sensor.

In some embodiments of the invention, the at least onetransducer-locating sensor comprises at least three transducer-locatingsensors a distance from the garment and the ultrasound processing unitis configured to provide spatial triangulation of various points alongthe garment from the at least three transducer-locating sensors.

In some embodiments of the invention, the at least onetransducer-locating sensor comprises at least one video cameraconfigured to record location of various points along the garment.

In some embodiments of the invention, the at least onetransducer-locating sensor occupying at least one position on thegarment comprises at least one of: a magnetic sensor, anelectro-magnetic sensor, and a radio frequency identification (RFID).

In some embodiments of the invention, the garment includes at least onefold that includes at least one of: an electronic sensor, and amechanical sensor, configured to measure spatial angles along the atleast one fold and transmit the spatial angles to the ultrasoundprocessing unit.

In some embodiments of the invention, the ultrasound processing unitadditionally includes a software module configured to process thespatial angles for at least one of: at least one sub-array, the at leastone array, a plurality of transducer arrays, and the at least onetransducer, located on each side of the one fold.

In some embodiments of the invention, the at least one transducercomprises one large ultrasonic array system and the ultrasoundprocessing unit includes a software module configured to receive dataand process data from the one large ultrasonic array system.

In some embodiments of the invention, the beam-forming unit is at leastone of: included in the garment, and located a distance from thegarment.

In some embodiments of the invention, the at least one ultrasoundtransducer comprises an “active” phased array which supports thegeneration of multiple receive beams in post ultrasound-receivingprocessing.

In some embodiments of the invention, the ultrasound processing unitincludes a software module configured to operate the “active” phasedarray.

In some embodiments of the invention, the ultrasound beam-forming unitis configured to support at least one imaging mode including at leastone of: reflection-based volume imaging, reflection-based ultrasoundcomputed tomography (UCT), reflection-based ultrasound diffractiontomography (UDT), reflection-based beam pairs, transmission-based UCT,and transmission-based UDT.

In some embodiments of the invention, the ultrasound processing unitincludes a software module configured to operate the ultrasoundbeam-forming unit such that the ultrasound processing unit receives andprocesses at least one mode including at least one of: transmitting, andreceiving at least one beam concurrently.

In some embodiments of the invention, the ultrasound processing unitincludes a software module configured to receive and process at leastone dataset of: 1D, 2D, and 3D.

In some embodiments of the invention, the receiving comprises at leastone of: time-dependent, and time-independent.

In some embodiments of the invention, the ultrasound processing unitincludes a software module configured to receive and process repetitivescans of at least one of: a plane, and a volume, at predefined angulardirections.

In some embodiments of the invention, the system includes at least oneof: a plurality of sub-arrays, and the plurality of transducer arrays,and wherein the ultrasound processing unit includes a software moduleconfigured to compound signals received to produce at least one outputdataset.

In some embodiments of the invention, the at least one dataset comprisesat least two datasets which are combined, thereby achieving at least oneof: extending a field of view, reducing speckle noise, improvingsignal-to-noise ratio, reducing shadowing artifacts, reducing clutterartifacts, enhancing spatial resolution, and enhancing image contrast.

In some embodiments of the invention, the at least two datasets arecombined according to a predefined logic.

In some embodiments of the invention, the ultrasound processing unitincludes a software module configured to provide computed tomographyimaging and using a data analysis system based upon obtainingmeasurements using at least one of: cylindrical geometry, and sphericalgeometry.

In some embodiments of the invention, the ultrasound processing unitincludes a software module-based process configured to comparereflections measured using opposite collinear beams to yield estimatesof at least one of: a local attenuation coefficient, and a local speedof sound.

In some embodiments of the invention, the ultrasound processing unitincludes a software module-based process configured to receive data fromcalibration beams, wherein the calibration beams include at least oneof: transmit beams, and receive beams, and the process aligns thetransmit beams and the receive beams.

In some embodiments of the invention, multiple strong reflectors areembedded in known positions along the garment, the strong reflectorsincluding at least one of: different shapes, and different reflectioncharacteristics, and the ultrasound processing unit includes a softwaremodule configured to discriminate between the strong reflectors.

In some embodiments of the invention, the ultrasound processing unitincludes a software registration module configured to receive data whichis one of: ultrasonic image based, sensor based, and ultrasonic imageand sensor based.

In some embodiments of the invention, the ultrasound processing unitincludes a software-based compounding module configured to produceoutput datasets from input datasets, wherein the input datasets compriseinformation from the provided beams, by: interpolating data for eachinput dataset to a coordinate grid of every output dataset, calculatinga weighted mean over all input datasets per output grid point, usinginput datasets whose field of view covers the relevant grid point.

In some embodiments of the invention, interpolation is performedsimultaneously to all input datasets.

In some embodiments of the invention, the weights for the weighted meanmay be computed according to various criteria, the various criteriaincluding at least one of: higher weights are assigned to input datasetswhose nearby pixels provide better lateral resolution, weights areassigned in inverse proportion to the effective volume of the relevantpixels within an input dataset, weights are assigned according to asignal-to-noise ratio estimate per input dataset, and low weights areassigned to datasets in which the local signal level is significantlylower than in the other datasets.

In some embodiments of the invention, the ultrasound processing unitincludes a software module-based process configured to provide at leastone of: averaging, and weighted averaging, which are assigned tomultiple datasets of several waveforms to reduce clutter effects.

In some embodiments of the invention, the assembly includes at least onetransducer, producing different waveforms, wherein the ultrasoundprocessing unit includes a software module-based process configured toprovide various functions of datasets acquired by the at least onetransducer at different waveforms that are calculated, thereby providinginformation with respect to local tissue type.

In some embodiments of the invention, statistical attributes of thewaveform dependent data are utilized, the statistical attributesincluding at least one of: average, weighted average, standarddeviation, and maximum to minimum ratio.

In some embodiments of the invention, the ultrasound processing unit isconfigured to receive input datasets acquired from multiple directions,and, for at least one small target region located in more than one ofthe input datasets, apply an elastic registration process to relevantmeasurements in the input datasets.

In some embodiments of the invention, the ultrasound processing unitextracts local attenuation coefficient measurements from outputs of theelastic registration process, wherein the elastic registration processis applied to at least two of the input datasets undergoing cumulativeattenuation along different paths, wherein the cumulative attenuationresults from local attenuation within the living body.

In some embodiments of the invention, the ultrasound processing unitextracts local speed of sound measurements from outputs of the elasticregistration process, wherein the elastic registration process isapplied to at least two of the input datasets undergoing cumulative timedelays along different paths, wherein the cumulative time delays resultfrom local attenuation within the living body.

In some embodiments of the invention, the elastic registration isperformed on at least one of: pairs of opposite collinear beams, andgroups of adjacent opposite collinear beams.

In some embodiments of the invention, in the pairs of opposite collinearbeams, the registration is reduced to a single dimension and searchingis done for specific patterns, including at least one of: maxima,minima, and other predefined patterns.

In some embodiments of the invention, the ultrasound processing unitincludes a software module-based process configured to reduce cluttereffects, including: acquiring at least one frame of data for the targetvolume, and for each sample range-gate at each beam position calculatinga beam pattern for the current range, with respect to an applicablescanning apex, at all other beam positions, wherein the beam pattern isnormalized so that the peak value is 1.0.

In some embodiments of the invention, the software module-based processis further configured to subtract from the sample range-gate measurementvalues at the same range, with respect to the applicable scanning apex,for all other beam positions, where each measurement value is multipliedby the corresponding beam pattern value.

In some embodiments of the invention, the software module-based processis further configured to subtract from the sample range-gate measurementvalues at the same range, with respect to the applicable scanning apex,for a group of other beam positions, where each measurement value ismultiplied by the corresponding beam pattern value, and wherein thegroup of other beam positions comprises beam positions for which atleast one value is high, the high value including at least one of: ameasurement, and the beam pattern.

In some embodiments of the invention, the software module-based processperforms iterative processing until a cessation criterion has been met.

In some embodiments of the invention, the ultrasound processing unitincludes a software module configured to utilize data from at least oneof: the at least one sub-array, the at least one array, the plurality oftransducer arrays, and the at least one transducer, to providepulsed-wave (PW) Doppler studies, wherein a full spectrum for a specificregion is acquired from multiple directions, thus extending theinformation provided.

In some embodiments of the invention, the ultrasound processing unitincludes a software module configured to utilize data from at least oneof: the at least one sub-array, the at least one array, the plurality oftransducer arrays, and the at least one transducer, to providecontinuous-wave (CW) Doppler studies, wherein at least two intersectingbeams, whose boresight directions over time may be at least one of:constant, and changing, are utilized to extract spatially dependentdata.

In some embodiments of the invention, the ultrasound processing unitincludes a software module configured to use Doppler shift measurementsfrom at least two points of view and reconstruct a 2D projection of a 3Dvelocity vector corresponding to the dominant velocity for at least onepixel.

In some embodiments of the invention, the ultrasound processing unitincludes a software module configured to receive Doppler shiftmeasurements from at least three points of view and reconstruct a full3D velocity vector for at least one pixel.

In some embodiments of the invention, an array of high intensitytransducers is integrated into the ultrasound garment and at least onethe high intensity transducer is at least one of: dedicated to highintensity focused ultrasound (HIFU) operation, and dedicated to imagingpurposes.

In some embodiments of the invention, the ultrasound processing unitincludes a software module configured to utilize at least one of: thelocal measurements of ultrasound attenuation, and the local measurementsof speed of sound, to adaptively optimize the beam-forming parameters ofthe high intensity transducers.

In some embodiments of the invention, the ultrasound processing unitincludes a software module configured to generate ultrasound computedtomography or ultrasound diffraction tomography images by geometricallytransforming at least one of: scanning processing parameters, and signalprocessing parameters, to obtain samples equivalent to those obtainedusing at least one of: cylindrical geometry, and spherical geometry.

In some embodiments of the invention, geometric transformation includesintroducing at least one equation of: phase delays, and time delays, toeach transducer component, wherein the at least one equation refers toat least one of: transmission, and reception.

In some embodiments of the invention, the assembly includes at least oneelectromagnetic radiation source, the at least one electromagneticradiation source occupying at least one position of: on the garment, andat a distance from the garment, and the at least one electromagneticradiation source includes at least one of: light source, andradio-frequency (RF) source.

In some embodiments of the invention, the ultrasound processing unitincludes a software module-based process configured to extract fromultrasonic reflections information regarding at least one of: localoptical absorption, and local RF absorption.

In some embodiments of the invention, the ultrasound processing unitincludes a software module-based process configured to perform at leastone of the following techniques: ultrasound computed tomography,ultrasound computed tomography with the geometric transformation,attenuation correction using the local attenuation coefficientmeasurements, and time-delay correction using the local speed of soundmeasurements.

According to another aspect of some embodiments of the invention, thereis provided, an ultrasound assembly, including: at least one ultrasoundtransducer array configured to be placed against a living body, anultrasound beam-forming unit operatively associated with the at leastone ultrasound transducer array, the ultrasound beam-forming unitconfigured to cause the at least one ultrasound transducer array toproduce and receive at least one pair of opposite collinear beams thatpass through the living body, an ultrasound processing unit operativelyassociated with the ultrasound beam-forming unit and configured toreceive and compare the at least one pair of opposite collinear beams toyield estimates of at least one of: a local attenuation coefficient, anda local speed of sound.

In some embodiments of the invention, the ultrasound processing unit isconfigured to apply an elastic registration process to relevantmeasurements of the at least one pair of opposite collinear beams, andfor each pair of opposite collinear beams perform at least one of:extract local attenuation coefficient measurements from outputs of theelastic registration process, wherein the pair of opposite collinearbeams, to which the elastic registration is applied, undergoescumulative attenuation along opposite beam paths, wherein the cumulativeattenuation results from local attenuation within the living body, andextract local speed of sound measurements from outputs of the elasticregistration process, wherein the pair of opposite collinear beams, towhich the elastic registration is applied, undergoes cumulative timedelays along opposite beam paths, wherein the cumulative time delaysresult from local variations in speed of sound within the living body.

In some embodiments of the invention, in pairs of opposite collinearbeams, the registration is reduced to a single dimension and searchingfor specific patterns, including at least one of: maxima, minima, andother predefined patterns.

According to still another aspect of some embodiments of the invention,there is provided, an ultrasound assembly, including: at least oneultrasound transducer array configured to be placed against a livingbody, an ultrasound beam-forming unit operatively associated with the atleast one ultrasound transducer array and configured to cause the atleast one ultrasound transducer array to produce and receive multipleultrasound signals through multiple small target regions in the livingbody, an ultrasound processing unit operatively associated with theultrasound beam-forming unit and configured to compare the multipleultrasound signals for each of the multiple small target regions toyield estimates of at least one of: a local attenuation coefficient, anda local speed of sound.

In some embodiments of the invention, the ultrasound processing unitincludes a software module configured to apply an elastic registrationprocess to the multiple ultrasound signals, and perform at least one of:extract local attenuation coefficient measurements from outputs of theelastic registration process, wherein the multiple ultrasound signals,to which the elastic registration is applied, undergo cumulativeattenuation along different paths, wherein the cumulative attenuationresults from local attenuation within the living body, and extract localspeed of sound measurements from outputs of the elastic registrationprocess, wherein the multiple ultrasound signals, to which the elasticregistration is applied, undergo cumulative time delays along differentpaths, wherein the cumulative time delays result from local variationsin speed of sound within the living body.

In some embodiments of the invention, the extraction is repeated for themultiple small target regions to provide a sound map of at least oneregion, including at least one of: a 2D region, and a 3D region.

In some embodiments of the invention, the extraction is repeated for themultiple small target regions to provide a 3D sound map and the softwaremodule is configured to: divide an output grid into layers taken atincremental ranges, determine a spatial map of at least one of:attenuation coefficients, and speeds of sound, and produce and correct areflection coefficient map.

In some embodiments of the invention, the software module isadditionally configured to produce and combine at least two of thefollowing maps: reflection coefficients, attenuation coefficients, andspeeds of sound, and provide tissue type classification data.

Unless otherwise defined, all technical and/or scientific terms usedherein have the same meaning as commonly understood by one of ordinaryskill in the art to which the invention pertains. Although methods andmaterials similar or equivalent to those described herein can be used inthe practice or testing of embodiments of the invention, methods and/ormaterials are described below. In case of conflict, the patentspecification, including definitions, will control. In addition, thematerials, methods, and examples are illustrative only and are notintended to be necessarily limiting.

Implementation of the method and/or system of embodiments of theinvention can involve performing or completing selected tasks manually,automatically, or a combination thereof. Moreover, according to actualinstrumentation and equipment of embodiments of the method and/or systemof the invention, several selected tasks could be implemented byhardware, software, or firmware; or by a combination thereof using anoperating system.

For example, hardware for performing selected tasks according toembodiments of the invention could be implemented as a chip or acircuit. As software, selected tasks according to embodiments of theinvention could be implemented as a plurality of software instructionsbeing executed by a computer using any suitable operating system.

In embodiments of the invention, one or more tasks according toembodiments of method and/or system as described herein are performed bya data processor, such as a computing platform for executing a pluralityof instructions. Optionally, the data processor includes a volatilememory for storing instructions and/or data and/or a non-volatilestorage, for example, a magnetic hard-disk and/or removable media, forstoring instructions and/or data. Optionally, a network connection isprovided as well. A display and/or an operator input device such as akeyboard or mouse are optionally provided as well.

BRIEF DESCRIPTION OF THE DRAWINGS

Some embodiments of the invention are herein described, by way ofexample only, with reference to the accompanying drawings. With specificreference now to the drawings in detail, it is stressed that theparticulars shown are by way of example and for purposes of illustrativediscussion of embodiments of the invention. In this regard, thedescription taken with the drawings makes apparent to those skilled inthe art how embodiments of the invention may be practiced.

In the drawings:

FIGS. 1A-1B show representations of an ultrasound system and operationalflow chart, respectively, according to some embodiments of theinvention;

FIG. 2 shows a single large ultrasonic array system, according to someembodiments of the invention;

FIG. 3 shows details of a portion of FIG. 2, according to someembodiments of the invention;

FIG. 4 shows an active phased array system, according to someembodiments of the invention;

FIG. 5 shows a single sub-array system, according to some embodiments ofthe invention. In some configurations, the ultrasound system may includea plurality of such sub-arrays;

FIG. 6 shows active phased array systems, according to some embodimentsof the invention;

FIG. 7 shows effective transducer geometry translation, according tosome embodiments of the invention; and

FIG. 8 shows graphs of peak location in collinear beam configurations,according to some embodiments of the invention.

DESCRIPTION OF SPECIFIC EMBODIMENTS OF THE INVENTION

The present invention, in some embodiments thereof, relates to fixingthe position of an ultrasound transducer with respect to a subject and,more particularly, but not exclusively, to fixing the position of anultrasound transducer within a garment affixed to the subject.

Before explaining at least one embodiment of the invention in detail, itis to be understood that the invention is not necessarily limited in itsapplication to the details of construction and the arrangement of thecomponents and/or methods set forth in the following description and/orillustrated in the drawings and/or the examples. The invention iscapable of other embodiments or of being practiced or carried out invarious ways.

Referring now to the drawings:

Ultrasonic Imaging System

In FIGS. 2-6, triangles stand for amplifiers or attenuators andcrossed-out circles stand for phase shifters and/or true time-delaycomponents. ‘S.A.’ stands for ‘Sub-Array’, ‘Sig. Gen.’ stands for‘Signal Generator’, and C_(i) ^(j) is the j'th channel of sub-array i.When two or more lines intersect, connections are denoted by small blacksingular dots.

Triplets of black circle symbols without numbers represent copies of theunits appearing in conjunction with the symbols, for example above andbelow the symbols.

FIGS. 1A-1B show representations of an ultrasound (US) system 100 andoperational flow chart 104 respectively which includes an ultrasoundgarment 110 affixed to a subject 102 and an ultrasound imager 112. Whilesubject 102 is depicted as a human being, the present invention may beused and/or configured for use on non-human animals.

Ultrasound garment 110 includes transducers 124, alternatively referredto as transducer components 124, fixed in position in ultrasound garment110 which, itself, is fixed in position with respect to subject 102.

Ultrasound garment 110 is alternatively referred to as affixedtransducer array 110, stationary ultrasound garment 110 or stationaryultrasound transducer garment 110.

The inventor has discovered that transducers 124 having relatively knownlocation and orientation may provide specific information that cancontribute to the quality of the reconstructed images, for example onimager 112, as will be explained below.

US system 100 optionally includes a beam-forming unit 120; a processingunit 122 and an operator-interface unit 114, alternatively referred toas user-interface unit 114. In FIG. 1B, data lines are shown asone-directional arrows. Control/status lines are shown astwo-directional arrows. Dashed lines relate to information which isoptionally present in some embodiments of system 100.

Beam-forming unit 120 generates the electronic signal fed intoultrasound garment 110. Transducers 124 in ultrasound garment 110transform the electronic signal into an ultrasonic signal, which withinbody of subject 102 undergoes, for example, attenuation, absorption,reflection, refraction, and dispersion.

The ultrasonic signal emanating from reflections and/or transmissionthrough the body of subject 102 is then sensed by transducers 124 inultrasound garment 110; which translate it into an electronic signalthat is sampled by beam-forming unit 120.

The digitized information is then processed by processing unit 122. Inembodiments, processing unit 122 also receives location and/ororientation information from ultrasound garment 110. Operator-interfaceunit 114 controls beam-forming unit 120; a processing unit 122, and alsodisplays information to the operator on imager 112. In some embodiments,said control of operator-interface unit 114 may be performed throughprocessing unit 122. Certain hardware configurations might combineultrasound garment 110 and beam-forming unit 120 into a front-end unit.

Beam-Forming Unit Details

Beam-forming unit 120 has two basic roles alluded to above:

-   -   i. Generating the electronic signal which drives transmitting        ultrasonic transducers 124, alternatively referred to as        transducer components 124. In embodiments, beam-forming unit 120        provides a separate signal to each transmitting transducer 124        or group of transducers 124.        -   In further embodiments, beam-forming unit 120 provides one            or more driving signals for each array of transducers 124 or            sub-array of transducers 124, as well as a set of parameters            controlling the signal attenuation and/or time-delay for            each transducer 124 or group of transducers. In the latter            case, the signal attenuation and/or time-delays, required            for forming the beams, are managed by ultrasound garment            110.        -   As used herein, the term “array” refers to an array of            transducers 124; while the term “sub-array” refers to a            sub-array of transducers 124 located within a larger array.    -   ii. Sampling the electronic signal produced by receiving        ultrasonic transducers 124. Diverse signal types are sampled in        different hardware configurations. In some cases, the signal        reaching each transducer 124 or group of transducers 124 may be        sampled. In other cases, one or more linear functions of some or        all of transducers 124 in an array or sub-array may be measured.        The linear combination may be performed by either ultrasound        garment 110 or beam-forming unit 120. The linear weights for        this linear combination can be predefined or calculated, and may        be determined by beam-forming unit 120, by ultrasound garment        110 based on inputs from beam-forming unit 120, or by ultrasound        garment 110 alone. Additionally or alternatively, the linear        weights for the linear combination can be calculated by        processing unit 122.

Garment Variations

There are a large number of designs and configuration of ultrasoundgarment 110. One ultrasound garment 110 embodiment, for example, isconfigured to partially or fully cover a certain body part, such as theabdomen or torso of subject 102.

Further, ultrasound garment 110 may be alternatively configured withdifferent shapes; each configured to cover a different portion of asubject; for example a pelvis, arm, foot, and/or a head.

Additionally, ultrasound garment 110 optionally is configured to covermultiple body parts, or even the entire body of a subject. The manyconfigurations possible for ultrasound garments 110 are easilyrecognized and appreciated by those familiar with the art of imaging.

In embodiments, ultrasound garment 110 is integrated into apparel, forexample a belt, a shirt, or a pair of pants.

Additionally or alternatively, ultrasound garment 110 optionallyincludes two or more parts, allowing more than one possible assemblyconfiguration, for example by separating one or more bands making upultrasound garment 110 prior to fixing the transducers in place.

Optionally, the surface of ultrasound garment 110 is continuous andconfigured to be easily molded to a given body part, for example as aninflatable cuff around the arm.

Alternatively ultrasound garment 110 optionally includes somediscontinuities. Additionally or alternatively, the surface ofultrasound garment 110 includes stretchable “seams” which can bestretched prior to fixation of the transducer positions.

In embodiments, ultrasound garment 110 optionally has an openconfiguration which may be adjustably closed around a body part. Forexample ultrasound garment 110 optionally includes a belt havingadjustable diameter, with a closure system comprising Velcro materialinterposed between the belt surfaces. Additional closure systemsoptionally include straps, tape, or clips.

In embodiments, ultrasound garment 110 optionally includes ultrasoundmedia designed for acoustic impedance matching between transducers 124and the body surface of subject 102. Such ultrasound media optionally,for example, include gel packs, covering parts of, or the entire innersurface of the apparatus. The gel packs optionally are disposable orrefillable. The media used for acoustic impedance matching optionallyincludes a gel. Additionally or alternatively, the media optionallyincludes a gas, liquid, or solid.

Garment Fixation

In embodiments, one or more fixation devices, such as straps, stickypatches or vacuum patches, optionally are used for keeping ultrasoundgarment 110 affixed in place.

In other embodiments, the fixation device is a part of transducers 124.For example, sticky surfaces or vacuum generating surfaces optionallyare used to maintain transducers in fixed positions.

Another option for maintaining position of transducers 124 is theaddition of a gas pocket providing negative pressure between the UStransducer array and the body surface, for example, along the innersurface of the apparatus. The pressure within such a gas pocketoptionally is adjusted to obtain a tighter or a looser fit of ultrasoundgarment 110.

In embodiments, the gas pocket is located along the outer surface of theapparatus and positive pressure, for example through inflation of thegas pocket, causes the transducers to be fixed in place.

Transducer Configuration

In some embodiments, ultrasound garment 110 optionally includes a largeUS transducer array; which may be divided into multiple sub-arrays. Suchsub-arrays optionally overlap each other in some configurations, whilein other configurations the sub-arrays are separate. In either case, thesub-arrays activation can be predefined or adaptively allocated by theimaging system.

The transducer array may, for example, comprise piezo-electric crystals.

The transmitting and/or receiving transducer components 124 optionallycover the entire ultrasound garment. Alternatively, the transmittingand/or receiving transducer components 124 optionally cover portions ofultrasound garment 110.

In embodiments, the transducer array covers ultrasound garment 110uniformly or non-uniformly.

Optionally, in embodiments, pluralities of transducer arrays are used.The arrays optionally are placed in close proximity to one another.Alternatively, the pluralities of transducer arrays optionally areplaced at a distance from each other.

In some embodiments, each of the multiple arrays has a separate casingor housing, and even a separate driving unit. In other embodiments,several arrays are housed together.

Irrespective of the number of arrays or sub-arrays, each array orsub-array optionally includes one or more transmitting and/or receivingtransducer components 124, ordered in a one-dimensional (1D),two-dimensional (2D), or multi-dimensional (MD) grid; wherein the gridpattern is Cartesian.

Alternatively, the grid pattern has a different pattern, for example,one or more hexagonal patterns. In still further embodiments, sparsegrids are utilized. In some embodiments, one or more acoustic lensesoptionally cover a sub-array, an array, or a group of arrays, eitherpartially or fully, for example to adjust the acoustic beam dimensions.

Each US transducer array and/or sub-array is optionally used to acquireultrasonic information regarding a certain line, a surface, or a volumewithin the subject's body.

An array or sub-array optionally scans a surface or a volumeelectronically and/or mechanically. Said mechanical scanning may beperformed, for example, by swinging, rotating, or oscillating the array,the sub-array, or even a group of transducers within the array orsub-array. In some cases, scanning is optionally electronic in a firstaxis and mechanical in a second axis.

Data acquisition is optionally performed over a short period of time.Alternatively, data acquisition is performed several times over a longerperiod of time, thereby providing time-dependent information.

In some embodiments, some or all of the transducer components 124,sub-arrays or arrays, are moved with respect to the surface ofultrasound garment 110, for example so as to enhance data acquisitionflexibility.

In embodiments, transducer components 124, sub-arrays or arrays can bemoved manually, for example, along special railings. In embodiments,detachable arrays are optionally fixed to multiple fixation points.Alternatively, motors may be utilized to change the location of thearrays, for example using rails with cog-wheels.

Location Sensors

Additionally or alternatively, ultrasound garment 110 includes one ormore location sensors or location sensor arrays 109 designed to providedata regarding the relative spatial location and/or orientation ofdifferent regions or transducer components 124 of ultrasound garment110.

The location sensors or location sensor arrays 109 optionally utilizeone or more of the many locating sensor technologies known in the art,for example:

-   -   i. In cases where ultrasound garment 110 has well defined axes        allowing folding, whether or not taking the form of actual axes,        the spatial angle between the surfaces on both sides of such        axes is optionally measured by electric sensors comprising, for        example, location sensor arrays 109.    -   ii. An optical stand-alone array 106 including one or more video        cameras placed beside ultrasound garment 110 optionally allows        spatial triangulation of various points along ultrasound garment        110.    -   iii. Magnetic or electro-magnetic location sensor arrays 109        attached to multiple locations along ultrasound garment 110        and/or placed as stand-alone arrays 106;    -   iv. A plurality of radio frequency identification (RFID) chips        location sensor arrays 109 mounted on ultrasound garment 110        which may optionally transmit to a base station (not shown).

As is known in the art, a group of three or more location sensors 109,mounted on a rigid surface, for example an ultrasonic array or asub-array; allows accurate estimation of both the location andorientation of that surface.

Conversely, if ultrasound garment 110 has known axes with degrees offreedom, less than three location sensors 109 may be required to fullyestimate the spatial location and orientation of each ultrasonic arrayor sub-array.

As described above, ultrasound transducers 124 are optionally configuredas having combined receiving and transmitting transducers. However,ultrasound transducers 124 may be configured with separate receiving andtransmitting transducers. The following narration describes just one ofthe many configurations of generating signals fed to transducers 124 andanalyzing the received signals.

Single Large Ultrasonic Array

FIG. 2 is an embodiment of a single large ultrasonic array system 250,which includes ultrasound garment 110.

Transducers 124 comprise a large ultrasonic array system which produceand/or receive ultrasound signals.

As a result of passing signals through a switching matrix 134, multiplesub-arrays are defined.

The result comprises M adaptively defined sub-arrays of transducer 124where each m'th sub-array (m varies between 1 and M) has N_(m) receivedatasets, and therefore, for example, N_(m) analog-to-digital (A/D)converters.

Ultrasound garment 110 and beam-forming unit 120, which includescomponents besides ultrasound garment 110, processing unit 122, andoperator-interface unit 114, may be used in configurations where thereception and transmission transducers 124 are combined or separate.

On transmit; the waveform produced by signal generator 132 optionallypasses through amplifiers and/or attenuators, as well as phase shifterand/or true time-delay devices, as shown in the figure by triangles, andcrossed-out circles as noted above.

This signal is fed to the transmitting transducer components 124 througha switching matrix 134, which adaptively allocates transmitting and/orreceiving transducer components 124 to data lines 176 as defined bycontroller 130.

On receive; the signal from each receiving transducer component 124 isdirected to the appropriate duplexer 140 using a controllable switchingmatrix 134, and may be amplified and/or attenuated, and in some casesundergo phase shifts and/or true-time delays.

The resulting signal from duplexers 140 enters Unit A 200 through datalines 178, as seen in detail in FIG. 3. In Unit A 200, 1:N_(m) splitters192 split signals from duplexers 140 (where m is the sub-array index).For every n_(m) between 1 and N_(m), the n_(m)'th output of eachsplitter can be further amplified or attenuated to adjust thesub-array's apodization pattern, and can also be fed through a phaseshifter or a time-delay device. The signals then enter the n_(m)'thcombiner 193.

The outputs of each combiner 193 are sampled by an A/D converter 190,and transferred to processing unit 122. Some or all of the amplifiers,attenuators, phase shifters, and true time-delay devices may be directedby controller 130.

In embodiments, the amplification/attenuation and/or the phaseshift/time-delay may be performed in two or more stages, located on oneor two sides of duplexers 140 (FIG. 2). Furthermore, both signalgenerator 132 and controller 130 or controllers 130 may be managed(controlled) by operator-interface unit 114 and/or processing unit 122.

Signals fed to and/or received from ultrasound transducers 124 may begenerated and/or analyzed in a variety of circuit configurations. Thefollowing narration describes just some of the many options for thesecircuit configurations.

Exemplary Circuit Configurations

FIG. 4 is an embodiment of an active phased array system 400, where anA/D converter 190 is assigned to each transmitting and/or receivingtransducer component 124 or group of transducer components 124. Such an“active” phased array supports the generation of multiple receive beamsin post-processing, without prior beam definition.

On transmit, the waveform produced by signal generator 132 passesthrough amplifiers and/or attenuators, as well as phase shifters and/ortrue time-delay devices, the parameters for all of which may becontrollable by a controller 130. This signal is fed to transmittingtransducer components 124.

On receive, the received signal may be amplified and/or attenuated, andmay also undergo phase shifts and/or true-time delays. The resultingsignal is sampled by A/D converter 190, and transferred to processingunit 122. Both signal generator 132 and controller 130 may be managed byoperator-interface unit 114 and/or processing unit 122.

FIG. 5 is an embodiment of a single sub-array system 500. In someconfigurations, the system may include a plurality of such sub-arrays.However, some or all of the following units may not necessarily beduplicated: the controller 130, the signal generator 132, the processingunit 122, and the user-interface unit 114.

On receive, the signal from each receiving transducer component 124 maybe amplified and/or attenuated, and may also undergo phase shifts and/ortrue-time delays. The resulting signal for each receiving transducercomponent 124 enters a 1:N splitter 194 (N may vary from one sub-arrayto another). For every n between 1 and N, the n′th output of eachsplitter can be further amplified or attenuated to adjust thesub-array's apodization pattern, and can also undergo phase shiftsand/or true-time delays. It then enters the n′th combiner.

The outputs of each combiner 192 are sampled by A/D converter 190, andtransferred to processing unit 122.

Both signal generator 132 and controller 130 may be managed byoperator-interface unit 114 and/or processing unit 122. In someembodiments, the amplification/attenuation and/or the phaseshift/time-delay may be performed in two or more stages, located on oneor two sides of the duplexers.

In all configurations, some arrays or sub-arrays can be used only fortransmitting or only for receiving, in which case duplexers are notnecessary. FIG. 6 is an embodiment of an “active” phased arrays system600, including a dedicated transmitter 610 and a dedicated receiver 620.

Dedicated transmitter 610 and dedicated receiver 620 have application,for example, in transmission mode UCT, and in ultrasound diffractiontomography (UDT) imaging modes which utilize pairs of sub-arrays 210 and310.

Each such pair includes a transmitting sub-array 224 and a receivingsub-array 324, which may, for example, generate opposite collinearbeams. Some or all receiving sub-arrays 324 may also receive reflectedor transmitted signals generated by other sub-arrays (not shown).

It should be understood that FIGS. 2-6 optionally include locationand/or orientation sensors 106 and 109, seen in FIG. 1, and respectiveprocessing.

In embodiments, a down-converter 630 may be added prior to the A/Dconverter, subtracting the frequency of the signal carrier provided bysignal generator 132, which may be constant or time dependent.Alternatively, down-converter 630 may set the center frequency to one ofthe signal carrier frequency's harmonics.

In other embodiments, the measured analog signal may be correlated tothe output of signal generator 132 in which a matched filter 632 isoptionally utilized, so as to provide pulse compression.

In some embodiments, the gain applied prior to sampling by the A/Dconverter may be automatically adjusted based on the measured signal (atechnique called “adaptive gain control”). The gain can also be timedependent (“time-gain control”), in order to decrease the dynamic rangeto be sampled, thus reducing the number of bits required by the A/D.Furthermore, in certain embodiments, the A/D converter may produce realsamples, whereas in other embodiments complex measurements are made.

Technologies relating to transducers 124 may include a variety oftechnologies other than planar arrays or phased arrays, in which casethe term “sub-array” should be interpreted as an ultrasound sourceand/or detector. The term “sub-array” may also indicate a first separatearray in conjunction with a second separate array.

Processing unit 122 may employ any technology known in the art. In somecases, it may be PC-based or any other suitable computing platform.Additionally or alternatively, one or more digital signal processors(DSPs), application-specific integrated circuits (ASICs) and/orfield-programmable gate array (FPGA) chips may be used. Thus, processingunit 122 may include hardware components and/or software modules.

Operator-interface unit 114 controls the other units according to theoperator's requirements. This may be performed either directly orthrough processing unit 122.

Operator-interface unit 114 may also receive status signals from theother units. In addition, this unit displays the operator selectedinformation, which can consist of alphanumeric information, measuredquantitative parameters, 2D or 3D anatomic and/or parametric images,various sections or projections of anatomic and/or parametric images andthe like.

Images and parameters may be time dependent. Pseudo-colors may be usedto describe functions of different parameters or a combination of two ormore parameters, for example the videointensity may describe oneparameter whereas the hue may describe another. Any display type, forexample a computer monitor or a 3D holographic display, may be used forthat purpose.

In some embodiments, some or all of the data and/or control cables maybe replaced with wireless communication of various types, using, forexample, Bluetooth of WIFI technology.

Adjustable Transducer Array Garment

Ultrasound garment 110 optionally uses a garment that includesultrasound transducer ports at multiple locations, to which the operatorselectively chooses and hooks up a variable number of transducers.

The transducer port locations may be predefined, manually adjustable, oradjustable using a motor. Motorized adjustment may be performed duringan examination, for automatically moving one or more probes over asurface, scanning a selected volume. Motorized adjustment may also beperformed before or after an examination, or during system modetransition. Adjustable transducer array garment optionally includes alocation and/or orientation sensor array described above.

The data obtained at multiple locations are recorded by the ultrasoundimaging system, and then analyzed either online or offline, using thetechniques described herein.

Beam-forming and Waveforms

Beam-forming may be described in terms of complex weights assigned todifferent transducers 124 of a transmitting and/or receiving sub-array.The complex weights are implemented, for example, by applying gainand/or attenuation, phase delays and/or time delays.

The complex weights may follow any suitable pattern. For example, thepattern of the gain of the transducer components 124 may follow aone-dimensional or a two-dimensional Hamming window. In someembodiments, the phase setting on transmit should be set to provide oneor more focal points. In this context, a focal point is a spatiallocation at which the phases of the signals generated by all relevanttransmitting transducer components 124 is equal to a certain constant,for example 0.

In further embodiments, the phase setting on receive should providedynamic focusing, i.e., the phases for each sample (range-gate) are setso as to assure that the overall time or phase delay along all pathsbetween the volume corresponding to the current sample and eachreceiving transducer component 124 is equal to a certain constant; forexample as described by Angelsen B A J; “Ultrasound Imaging—Waves,Signals and Signal Processing”; Emantec A S, Trondheim, Norway 2000;I:1.34-1.44.

The system may utilize any waveform known in the art, including bothpulsed wave (PW) and continuous wave (CW) transmission. In embodiments,rectangular pulses may be used. Optionally, coded excitation techniquesmay be used, such as linear or non-linear frequency modulation; binarysequences, for example, Barker codes, Allomorphic forms andcomplementary sequences; and poly-phase codes; as described by Skolnik MI; “Radar Handbook”; McGraw-Hill, Boston, Mass. 1990; 10.1-10.39.

Furthermore, in embodiments, different coded excitation techniques orapproximately orthogonal sequences of the same coded excitationtechnique may be fed to different transducer components. This allows,for example, dynamic focusing and/or dynamic aperture setting ontransmit, as mentioned by Zheng Y, Silverstein S D; “Novel TransmitAperture for Very Large Depth of Focus in Medical Ultrasound B-scan”;IEEE Transactions on Ultrasonics, Ferroelectrics, and Frequency Control2006; 53:1079-1087.

System Modes

Numerous configurations of transmission and/or reception transducercomponent allocations may be considered for ultrasound garment 110-basedsystems. At any given time, P sub-arrays may be assigned to transmit andQ sub-arrays may be assigned to receive; P and Q are parameters whichmay or may not be equal, and can change over time. Some of thesesub-arrays may perform both transmission and reception.

Furthermore, a certain receiving transducer sub-array may providemultiple receive datasets; for example, use multiple A/D converters;each of which can relate to different beam configurations.

Different beam configuration include, for example, differences in beamwidth, boresight direction, receive gain, and/or central frequency.

In some embodiments, one or more of the following basic modes, describedhereinbelow, can be supported:

-   -   i. Reflection-based volume imaging.    -   ii. Reflection-based UCT.    -   iii. Reflection-based UDT.    -   iv. Reflection-based beam pairs.    -   v. Transmission-based UCT.    -   vi. Transmission-based UDT.

The reflection-based volume imaging and the reflection-based beam pairsmode are also referred to as the “fundamental reflection modes”.

For each mode, data for the target volume or for parts of that volumemay be obtained once. Alternatively, it may be collected as a functionof time. When time-dependent information is gathered for organs showingcyclic motion, such as the heart, applicable measurable biologicalsignals, for example electrocardiography signals, may be utilized toimprove image quality. Such procedures are usually referred to as gatingtechniques. For example, the cycle may be divided into K intervals, andthe data for each interval may be integrated over multiple consecutivecycles.

In some cases, data may be collected for partial volumes, which may bedefined by the operator or selected automatically following variouscriteria. The partial volume covered may also change over time. Dataacquisition for partial volumes usually requires using fewer beams tocover the scanned volume, and thus allows increased refresh rates, whichare especially useful in applications where the target organ moves overtime, for example cardiac imaging or gastro-intestinal imaging.

In further embodiments, two or more of the above described imagingmodes, for example reflection-based volume imaging andtransmission-based UCT may be combined, and applied in either concurrentor alternating fashion. In such cases, the processes for the two or moreimaging modes will be applied.

Additionally or alternatively, tailored processes may be defined forthese combined modes. For instance, transmission-based measurements,examples for which are attenuation and time delay measurements, mayprovide a reference for various reflection-based processes, performingoperations such as attenuation correction or corrections for speed ofsound variability. Special display configurations may be devised for thecombined modes, providing the operator with various functions orrepresentations of the information obtained.

Transmitting and/or receiving a plurality of beams concurrently mayreduce the overall time required to cover the target volume or partialvolume. However, when two or more beams are transmitted at the same timeor approximately at the same time, especially if the beams' main-lobescover spatially adjacent volumes, some mutual interference may occur. Inorder to prevent such mutual interference, different concurrent beamsmay use different transmission frequencies.

Additionally or alternatively, concurrent beams may use different codedexcitation patterns, for example dissimilar linear frequency modulationpatterns.

Reflection versus Transmission Imaging

As mentioned hereinabove, reflection modes provide an array of timedependent echo measurements. Given the approximate local speed of sound,time dependence may be translated into range dependence. Thesemeasurements are correlated to the local reflection coefficient, butalso are affected by the two-way cumulative attenuation along the beam,up to the relevant reflecting volume of tissue.

Conversely, transmission modes usually provide only two scalarparameters for each beam—an estimate of the speed of sound, and thetotal signal attenuation along a beam.

Furthermore, the beam configuration for reflection and transmissionmodes is different. In reflection modes, the transmitting sub-array isoften used for receiving as well. In some cases, additional adjacentsub-arrays, located on the same side of the subject, are used to receivethe reflected signal as well. In comparison, in transmission modes, oneor more receiving sub-arrays are assigned to each transmitting array.The transmitting and receiving sub-arrays are located on opposite sidesof the subject.

In transmission-based UCT, a receive beam should be paired with eachtransmit beam. The two beams should be collinear or close to collinear,and also temporally synchronized.

Reflection-Based Volume Imaging

This mode is based on acquiring 1D, 2D, or 3D datasets, which may or maynot be time-dependent, by multiple sub-arrays (or arrays). Eachsub-array may be 1D, 2D, or MD, and can scan a target volume using anyscanning pattern. The origin of all beams produced by a sub-array isreferred to as the “phase center” or the “scanning apex”. In some cases,one or more transmitting and/or receiving transducer components may beincluded in more than one sub-array. In some embodiments, the systemrepetitively scans a plane or a volume at predefined angular directions,for example equidistant azimuth and/or elevation angles, using one ormore scanning apexes.

The data acquired by all sub-arrays is compounded to produce one or moreoutput datasets. In some embodiments, an output dataset may cover thecombined volume of all acquired datasets, thus extending the field ofview. In some further embodiments, only regions covered by severalsub-arrays (or “views”), as determined according to a predefined logic,are included in the output datasets.

Ultrasound Computed Tomography (UCT)

The inventor has discovered that ultrasound garments may haveapplication in UCT and UDT imaging. The following description presentsjust some of the many possible means of extracting information toprovide UCT and UDT imaging data.

Currently available reflection mode or transmission mode UCT systemsusually utilize cylindrical geometry, i.e., the transmitting and/orreceiving sub-arrays are placed on the surface of an approximatecylinder. Ultrasound garment 110 systems provide a more generalizedgeometry, which usually cannot be determined prior to outfitting thesubject with the system.

In order to solve the new, more complex geometry, the inverse problemequations may be rewritten and solved. Additionally or alternatively,one can adjust the scanning and/or signal processing parameters toobtain samples equivalent to those obtained using, for example,cylindrical or spherical geometry (this method is referred tohereinbelow as the “geometry emulation algorithm”). Once theseadjustments are made, any inverse problem method, and especially any UCTtechnique, which are known in the art, may be applied. These methodsinclude, for example, iterative back-projection, filteredback-projection, and analytic reconstruction; for example as describedby Louis A K; “Medical Imaging: State of the Art and FutureDevelopment”; Inverse Problems 1992; 8:709-738.

The geometry transformation may be performed by introducing phase and/ortime-delays to each transmitting and/or receiving transducer component,which are set so as to emulate the transmission and/or reception of thesignal from a transducer component placed on the surface of apre-selected 3D geometric shape. In an embodiment, this shape is acylinder, whose diameter is equal to or greater than the maximaldistance between any pair of sub-arrays (or transmitting/receivingtransducer components). The one-way (transmit or receive) time-delay Δtrequired for effectively translating the location of a transmittingand/or receiving transducer component, whose location with respect tothe center of the current range-gate is {right arrow over (r)}, to a newlocation {right arrow over (r)}′, given in the same coordinate system,is:

${\Delta \; t} = \frac{\left( {{{\overset{->}{r}}^{\prime}} - {\overset{->}{r}}} \right)}{c}$

where c is the speed of sound in the medium. Similarly, the one-wayphase delay Δφ is given by:

${\Delta \; \varphi} = {2\pi \; {{mod}\left\lbrack {\frac{\left( {{{\overset{->}{r}}^{\prime}} - {\overset{->}{r}}} \right)}{\lambda},1} \right\rbrack}}$

where λ is the transmitted or received wavelength and ‘mod’ stands forthe modulus operator. If the same transducer component both transmitsand receives, the time-delay and/or phase delay should be doubled.

The effective location of each transmitting and/or receiving transducercomponent may be set according to different criteria. For example, inreflection mode, for each range-gate, the transducer component may beeffectively placed at the intersection point between the selected 3Dgeometric shape and a line connecting its actual location with thecenter of the range-gate, as explained below with respect to FIG. 7.Another solution is translating the effective location of thetransmitting and/or receiving transducer component to the surface of the3D geometric shape along a line parallel to the beam's boresight, whichgoes through the transducer component's actual location.

Transducer Component Translation

FIG. 7 shows a configuration of effective transmitting and/or receivingtransducer component translation 700, according to an embodiment of thepresent invention. For convenience purposes, a 2D case is used. Theactual surface of ultrasound garment 110 is shown as a black dashedline, whereas a selected 3D geometric shape 180 is shown as a blacksolid line. Arrows 182 show the translation required in this case forseveral transducer component locations. Dotted lines connect thetransducer components with the center of the range-gate.

This transformation requires knowing the actual location and/ororientation of each transmitting and/or receiving transducer component.This information may be based on a sensor array, but may also use othertechniques, described in the “Coordinate System Registration” subsectionbelow. Once this information is available, it may also be used duringreconstruction as a constraint over the solution: there is no reflectionor attenuation outside the actual surface of ultrasound garment 110.

Additionally or alternatively, dummy ‘0’ measurements may be added inreflection modes for regions outside the actual surface of ultrasoundgarment 110.

In addition, this transformation changes the effective area of thesub-array, and may therefore affect beam width (in both axes), angularresolution, and signal-to-noise ratio (SNR). In some embodiments, theshape and dimensions of the sub-array may be adjusted to provide morehomogeneous angular resolution and SNR over different beams.

Ultrasound Diffraction Tomography (UDT)

Unlike UCT, UDT requires that for each transmit beam, multiplemeasurements would be made on receive, using a plurality of phasecenters and/or beam directions.

As in the case of UCT, one may solve the new inverse problem equations,and/or adjust the system to produce data equivalent to that obtained incylindrical geometry platforms (or platforms of other geometries), usingthe techniques described in the previous subsection “TransducerComponent Translation”.

Beam configuration design for UDT modes is often quite complex. Thephase center location and orientation of the various receive beams withrespect to the relevant transmit beam may be constant, but it may alsochange over spatial location or time. For instance, the spatial anglesformed between the transmit beam and each of the relevant receive beamsmay be kept constant. Another possibility is to keep a constant distancebetween the phase centers over ultrasound garment 110 surface. Moreover,in some embodiments, the orientation of the receive beams may adaptivelychange during data acquisition per pulse. For example, all receive beamsmay be directed at a point along the transmit beam, which is scannedover time.

Reflection-Based Beam Pairs

In embodiments, one can obtain additional information by comparing thereflections measured along opposite collinear beams. Examples for suchadditional information, which can be obtained using methods describedhereinbelow, are estimates of the local attenuation coefficient, orlocal speed of sound.

Generating opposite collinear beams in ultrasound garment 110-basedsystems, where the data acquisition geometry changes between differentsubject 102s and even different examinations, requires precise knowledgeof the relative location and/or orientation of different transducercomponents and/or sub-arrays, as well as accurate control over thescanning apex location, and the directionality of transmit and receivebeams. Methods for evaluating the location and/or orientation oftransducer components and/or sub-arrays are described in the “CoordinateSystem Registration” subsection below. These methods also includespecial calibration beams, which may be utilized for collinearityoptimization. Various ultrasound garment 110 hardware configurations, asdescribed hereinabove, can provide adequate control over apex locationand beam directionality.

Applicable Processes

In various embodiments, one or more of the following processes may beapplied to the acquired data:

-   -   i. Processing per receive dataset—processing applied directly to        each receive dataset, i.e., to the outputs of each A/D        converter.    -   ii. Coordinate system registration—matching the coordinate        systems of data acquired by multiple sub-arrays (or arrays) or        by one or more sub-arrays at different time frames.    -   iii. Compounding—combining the data obtained from multiple        sub-arrays or from one or more sub-arrays at different time        frames to form one or more new datasets.    -   iv. Further processing may be applied for display purposes,        according to the operator's requirements.

Examples of such processes are given in the current section. It shouldbe emphasized that the use of all these processes is not restricted toultrasound garment 110 systems as described herein, but rather may beexpanded to any ultrasound imaging system where data is acquired atmultiple positions and/or tilts, using one or more imaging probes, andthe data from the multiple positions and/or tilts is combined andcompounded to generate one or more datasets, which may be one-, two-, orthree-dimensional, and either time dependent or time independent.

Processing Per Receive Dataset

The processing per receive dataset may use any suitable technique knownin the art. Some processing steps are:

-   -   i. Logarithmic compression—the magnitude or squared magnitude of        the sampled data may be converted into logarithmic units, for        example decibels, in order to reduce the dynamic range.    -   ii. Time-gain control (TGC)—time (range) dependent gain        corrections may be applied. These corrections may be performed        in hardware, software, or a combination thereof. The parameters        of these corrections may be set by the operator, but may also be        automatically determined.    -   iii. Dynamic range windowing—mapping all values to a range        between predefined minimal and maximal values. Values lower than        a certain threshold may be set to the minimal value, whereas        values higher than another threshold may be set to the maximal        value.    -   iv. Brightness transfer function (BTF)—applying certain        predefined or adjustable functions to the values. These        functions are usually aimed at improving the contrast for        specific ranges of signal level.

Coordinate System Registration

As mentioned above, registration may be defined as a process mapping anypoint in one coordinate system to the corresponding point in anothersystem. This mapping may be spatial and/or temporal. Ultrasound garment110-based systems provide three potential sources for location and/ororientation information, each of which may provide time dependentinformation:

-   -   1) The sensor array, if included in the system, provides direct        estimates of location and/or orientation for multiple sub-array        or array transducer components. However, the accuracy of these        estimates is fairly limited.    -   2) A higher degree of information accuracy may be obtained with        special beam configurations (“calibration beams”). In some        cases, the calibration beam design may be founded on the        assumption that when a transmit beam and a receive beam are well        aligned, the transmission mode and perhaps the reflection mode        signal levels are expected to be higher than in other,        non-aligned scenarios. Configurations include:        -   i) In transmission UCT mode, several receive beams, having            slightly different orientations and/or apexes, may be used            per transmit beam. By selecting the receive beam producing            the highest signal intensity, one can align the receive beam            with the transmit beam. Such measurements can also be            performed iteratively, decreasing the orientation and apex            location diversity between consecutive steps.        -   ii) The same technique may be applied to the transmit beam            and the central receive beam in transmission UDT mode, which            are supposed to be collinear.        -   iii) Similarly, in reflection-based volume imaging, the            angular location of a second sub-array's phase center with            respect to a first sub-array's phase center may be estimated            as follows: the second sub-array should transmit several            calibration pulses towards the general direction of the            first sub-array. The second sub-array thus “draws a line”            over the image acquired by the first sub-array, which can be            detected and directionally analyzed.    -   In further cases, the calibration beams may utilize the        assumption that when two beams are aligned, the transmitted        and/or reflected signal for the two beams is best matched. Some        configurations:        -   i) In UCT mode, one may switch the roles of the transmitting            and the receiving sub-arrays. When the two beams are            perfectly aligned, such a switch should have negligible            effect on both the overall attenuation and the mean speed of            sound measured. Some minor mismatch is still expected,            mainly due to noise.        -   ii) The same technique may be applied to the transmit beam            and the central receive beam in transmission UDT mode, which            are supposed to be collinear.        -   iii) In reflection-based beam pairs mode, when a pair of            beams is precisely aligned, and after flipping one of the            datasets, the range-dependent signal for the overlapping            portion of the beams should be very similar, since the two            sensors are placed on opposite sides of the subject.        -   The difference between the two datasets is expected to            primarily result from differences in cumulative attenuation            and time delays along the beams. In order to minimize the            effect of these differences when comparing the two datasets,            one may also apply local pattern recognition techniques or            calculate various functions of local correlation            coefficients, rather than simply calculate the overall            correlation between pairs of datasets.    -   In some embodiments, one or more calibration beams can be        transmitted when the subject is outfitted with ultrasound        garment 110, or upon mode transition. Calibration beams may also        be transmitted at certain time intervals during the ongoing        operation of various modes, so as to correct for location and/or        orientation changes over time.    -   3) The acquired image data, to which software-based registration        techniques may be applied, also providing information regarding        the location and/or orientation of multiple sub-arrays or array        transducer components. The acquired image data is formed        directly in reflection-based volume imaging. Alternatively,        acquired image data may be formed in reflection-based beam pairs        mode.    -   In other modes, 2D and/or 3D images are usually generated by        reconstruction techniques applied to data acquired by multiple        sub-arrays. Such reconstruction techniques may also be utilized        in reflection-based beam pairs mode. In these cases, short        bursts of reflection-based volume imaging may be used for        coordinate system registration. Additionally or alternatively,        in UCT or UDT modes, multiple small changes in the orientation        and/or location estimate for every sub-array may be introduced        prior to reconstruction, and the configuration providing the        sharpest overall image should be selected.

In certain embodiments, transducer components having a very highreflection coefficient (“strong reflectors”) may be embedded in knownpositions along ultrasound garment 110. Different strong reflectors mayhave different shapes or different reflection characteristics, so as toallow discrimination between them. In reflection-based modes, strongreflectors should be well visible in the obtained image, assuming thecoverage volume includes ultrasound garment 110's surface. Such strongreflectors thus provide additional information concerning the relativeposition and/or orientation of various transmitting and/or receivingtransducer components or sub-arrays.

In some embodiments, data provided by two or more of the abovementionedsources is combined or fused. Data fusion may be performed using anytechnique known in the art. For example, if a sensor array is presentand/or calibration beams are transmitted, their measurements may be usedto initialize a software-based registration process. Additionally oralternatively, linear or non-linear combinations of the differentestimates can be used. For instance, the final estimated location and/ororientation may be set to the software solution if the differencebetween the two estimates is lower than a predefined value. Otherwise,the final estimated location and/or orientation would be set to thesensor array (and/or calibration beam) measurement.

Software-Based Registration

As mentioned hereinabove, the image in UCT and UDT modes isreconstructed using multiple sub-arrays. Therefore, this subsectionrelates especially to the fundamental reflection modes.

Software-based registration methods may be coarsely divided into twogroups rigid registration and elastic registration. Rigid registrationassumes that the two or more datasets registered describe a rigid body,so that only global translation and rotation of the datasets arerequired; for example as taught in U.S. Pat. No. 6,159,152; Dec. 12,2000, by Sumanaweera T S, Pang L, Bolorforosh S S; “Medical DiagnosticUltrasound System and Method for Multiple Image Registration”. Elasticregistration also allows for local deformation, for example due to softtissue deformation, in motion of subject 102 or organ motion, asdescribed by Krücker J F, LeCarpentier G L, Fowlkes J B, Carson P L;“Rapid Elastic Image Registration for 3-D Ultrasound”; IEEE Transactionson Medical Imaging 2002; 21: 1384-1394.

Each process may utilize one or more similarity measures, for example,mutual information measures, correlation coefficient on intensity valuesor on gradient images, and intensity values using optic flow hypothesis.In some cases, the registration accuracy may be better than the spatialresolution, in which case it is referred to as “sub-pixel resolution”registration. Within this document, the term “pixel” relates to picturetransducer components of 1D, 2D, and 3D datasets. The term “voxel”,sometimes referring to 3D picture transducer components, is not used.

In the fundamental reflection modes, for each frame (or time-frame), thedatasets registered are obtained approximately at the same time.Consequently, one may assume that the 1D, 2D, or 3D images describecertain regions of a large rigid volume, and thus apply rigidregistration techniques, using, for example, sub-pixel resolution.

However, since the speed of sound changes from one medium to the other,the time difference between the pulse generation and the arrival of thereflected signal, which is used to estimate the reflector's distancefrom the US transducer array 110 or sub-array, also depends on thetissue types along the beam path; and therefore on the beam path itself.Elastic registration techniques can therefore provide more accurate oradditional information. In some cases, a single registration step may beapplied, which is either rigid or elastic. In other cases, tworegistration steps may be used: rigid registration, followed by elasticregistration, which improves overall performance, and can also providean input to further data extraction processes.

In cases where the target organ moves significantly during dataacquisition, the dataset acquired should be time dependent, and temporalregistration should also be employed, for example usingelectrocardiography (ECG) gating.

Data Compounding

Data compounding techniques for both reflection-based andtransmission-based UCT and UDT modes were mentioned in the “SystemModes” section above. The current subsection relates mainly to thefundamental reflection modes.

Fundamental Techniques

Once spatially dependent datasets have been obtained by severalsub-arrays for a certain time frame, these “input datasets” may becompounded to produce one or more “output datasets”, each of whichproviding information regarding a predefined coordinate grid. Thesegrids can be Cartesian, but other grid types, for example hexagonal,helical, or spherical grids, may also be used. The grid of the outputdatasets may cover a substantially larger volume than any input datasetgrid, thus providing an extended field of view.

A possible compounding method can be based on interpolating the data foreach input dataset to the coordinate grid of every output dataset, andthen calculating the weighted mean over all input datasets per outputgrid point; in which case only input datasets whose field of view coversthe relevant grid point should be considered.

Alternatively, interpolation may be performed simultaneously to alldatasets. Any interpolation technique known in the art can be used forthese purposes, for example, linear interpolation, cubic interpolation,and cubic smoothing spline. As a result of such spatial averaging, theoutput dataset is expected to include lower speckle noise and thermalnoise levels. Image contrast may also be improved as a direct result.Furthermore, given sufficient data, accurate information may beascertained for an output grid in which the distance between adjacenttransducer components is smaller than that in the input datasets, sothat the resulting spatial resolution would be superior to that in theinput datasets.

When interpolation is applied separately to each input dataset, theaveraging weights may be computed according to various criteria. Someexamples:

-   -   i. In ultrasound imaging, each sub-array usually produces        approximately constant axial (range dependent) resolution, but        the lateral (cross-range) resolution may worsen as the distance        from the transducer increases. This is a result of using        spherical scanning configurations; for example beam steering in        azimuth and/or elevation. In addition, when beam steering        techniques are used with a constant-size sub-array, the beam        width usually increases with the off-broadside angle. Therefore,        per output grid point, higher weights can be assigned to input        datasets whose near-by pixels provide better lateral resolution.        Alternatively, the weights may increase, for example in inverse        proportion, as the effective volume of the relevant pixels        within an input dataset decreases.    -   ii. The local SNR per sample in each dataset is a function of        various parameters, including, inter alia, the transmission        frequency; the distance from the transducer; the beam steering        spatial angle; and the cumulative attenuation along the beam,        which increases with the distance from the transducer. To obtain        optimal results, the averaging weights can also depend on the        local SNR estimate per dataset.    -   iii. In some cases, highly absorbent or reflective regions        within a sub-array's coverage area may cause shadowing in the        image, i.e., substantially reduce the signal levels received        from scanned regions located behind them along the relevant        ultrasound beams. In order to cope with this effect, low weights        may be assigned to datasets in which the local signal level is        significantly lower than in the other datasets. A variety of        operators may be applied for this purpose. For example, the        signal level may be compared to the local arithmetic or        geometric average over all datasets, the median over all        datasets, a certain percentile of the datasets, or the average        over all datasets plus a certain multiple of the standard        deviation over all datasets.

Overall performance may be enhanced by the following iterative process:

-   -   i. Calculate an output dataset, according to the methods        described hereinabove.    -   ii. Interpolate the output dataset in order to estimate the        values for every grid point of each input dataset.    -   iii. Compare the results to the input datasets, and update the        output dataset accordingly. For example, very large differences        between an input dataset and an interpolated output dataset may        be detected, following a local update of that region within the        output dataset.    -   iv. If certain cessation criteria, for example maximal number of        iterations, or negligible changes in the output dataset over the        last iteration, have not been met, return to step ii.

Multi-Frequency Datasets

As mentioned before, multiple sub-arrays may transmit simultaneously orapproximately simultaneously, using orthogonal or almost orthogonalwaveforms. Scanning each small region within a target volume by multipletransmission frequencies or waveforms may also be used to extractadditional or improved information.

One aspect of this matter relates to the fact that, for a givensub-array configuration, the beam pattern changes with the transmissionwaveform. Therefore, highly reflective transducer components in the beamside-lobes, causing side-lobe clutter (also discussed below), contributedifferently to the samples in different waveforms. Averaging or weightedaveraging over datasets of several different waveforms can thus reduceclutter effects.

Another aspect is tissue classification. For each grid point of anoutput dataset, various functions of the adjacent input dataset gridpoints of different waveforms can be calculated, providing informationregarding tissue type. For example, statistical attributes of thewaveform dependent data, such as standard deviation or maximum tominimum ratio, can be utilized.

Inaccuracies in the time-gain control (TGC) process, applied prior todata compounding, may introduce errors into the measurements for one ormore waveforms, and consequently skew the tissue classification results.

Attenuation Correction

Signal attenuation in ultrasound imaging is usually described in termsof a local attenuation coefficient λ(r,θ,φ) (r, θ and φ are the threespherical coordinates), whose effect on reflected echo measurement iscumulative in logarithmic units. The effective one-way (transmit orreceive) energy attenuation factor for a distance R along a beam whoseboresight points at a spatial angle (θ,φ), is given by:

exp [−∫₀^(R)λ(r, θ, φ)r].

When the signal energy is given in logarithmic units, for example indecibels, the effective one-way energy attenuation factor is:

−∫₀^(R)λ(r, θ, φ)r.

The integral is often replaced by summation over discrete values.

A local attenuation coefficient map may be derived from the outputs ofthe transmission-based UCT mode. By activating both this UCT mode and areflection-based mode at a certain sequence, for example at interleavingframes, one may use the UCT-based attenuation map to correct thereflection-based map. However, this process increases the dataacquisition duration per frame, and thus increases system sensitivity tomotion of the subject and/or the imaged organ.

In some embodiments of the invention, local attenuation measurements,which provide important spatially and/or temporally dependent clinicalinformation, and allow improving ultrasound images by applying localattenuation correction, may be performed using only reflection-basedinformation. The following is an explanation of just one method forproviding local attenuation measurements for an ultrasound garment ofthe present invention; as well as existing ultrasound imaging systems.The main concept underlying this method is that elastic registrationbetween multiple input datasets can provide multiple logarithmic energymeasurements m_(q) (q is the dataset index) for each small targetregion, located in all input datasets by registration. Each of thesemeasurements m_(q) undergoes cumulative attenuation along a differentpath {right arrow over (r)}_(q). Data acquisition geometry is generallyknown, so that a set of equations may be written, describing therelationships between λ(r,θ,φ) values for different regions. Forexample, for a single small target region, viewed by two paths {rightarrow over (r)}_(q1) and {right arrow over (r)}_(q2):

${{\int_{{\overset{->}{r}}_{q\; 1}}{{\lambda \left( {x,y,z} \right)}{r}}} - {\int_{{\overset{->}{r}}_{q\; 2}}{{\lambda \left( {x,y,z} \right)}{r}}}} = {m_{q\; 2} - m_{q\; 1}}$

where (x, y, z) is a Cartesian coordinate system. This equation isreferred to as the “two-path attenuation equation”.

One possible geometry used for solving this problem is based on pairs ofopposite collinear reflection beams, which are also provided by thereflection-based beam pairs mode. First of all, the data for the twobeams has to be registered to a single coordinate system with an axialdimension x (ranging between 0 and X), yielding two registered datasetsm₁(x) and m₂(x). Since the overall side-to-side attenuation, λ_(tot),should be equal in both datasets, it can be easily shown that:

$\begin{matrix}{{m_{1}(x)} = {{r(x)} - {\int_{0}^{x}{{\lambda (y)}{y}}}}} \\{{m_{2}(x)} = {{r(x)} - {\int_{x}^{X}{{\lambda (y)}{y}}}}} \\{= \left. {{r(x)} - \lambda_{tot} + {\int_{0}^{x}{{\lambda (y)}{y}}}}\Rightarrow{r(x)} \right.} \\{= {\frac{1}{2}\left\lbrack {{m_{1}(x)} + {m_{2}(x)} + \lambda_{tot}} \right\rbrack}} \\{{\int_{0}^{x}{{\lambda (y)}{y}}} = {\frac{1}{2}\left\lbrack {{m_{2}(x)} - {m_{1}(x)} + \lambda_{tot}} \right\rbrack}}\end{matrix}$

where r(x) is the true reflection coefficient along the axial dimension.These equations, referred to as the “collinear attenuation equations”,are only precise for a noise free environment, but are expected toprovide acceptable results in real scenarios as well.

In the reflection-based beam pairs mode, elastic registration may beperformed either on pairs of opposite collinear beams or on groups ofadjacent opposite collinear beams. In the first case, the registrationis reduced to a single dimension. As a result, one may look for specificpatterns, which should be located in the two beams, for example maximaor minima.

All the located patterns in one beam should be located in the other oneas well, as will be explained with respect to FIG. 8.

FIG. 8 shows graphs of opposite collinear beams 800 having peaks, asprovided by the reflection-based beam pairs mode, including:

a true reflection coefficient graph 810 along the beam;

a left to right reflected signal graph 820, meaning that the reflectedultrasound is measured when looking from left to right; and

a right to left reflected signal graph 830, as measured when lookingfrom right to left.

In graph 810, true reflection peak locations are marked by dashed lines812 and 814. Dashed lines 812 and 814 are extended through left to rightreflected signal graph 820 and right to left reflected signal graph 830;in which offsets in peak location are caused by time delays within thetissue with respect to the nominal speed of sound, whereas peak leveldecrease results from cumulative attenuation.

The signal levels at the locations of the peaks or other detectedpatterns, as determined in the left to right reflected signal and in theright to left reflected signal, may be used to compute the localattenuation coefficient λ(x) for various intervals of axial dimension x,using the collinear attenuation equations. One can assume that theattenuation coefficient λ(x) is homogeneously spread over regionsbetween adjacent detected peaks or other patterns. This computation maybe repeated for multiple beam pairs, thus providing an attenuationcoefficient map for a 2D or 3D region.

This process is only applicable if full side-to-side information hasbeen obtained for all applicable beam pairs. In other cases, one cangenerate an attenuation coefficient map for all volumes covered by beampairs with full side-to-side coverage, and then iteratively use this mapto complete missing information in beams with partial coverage.

In another embodiment, the output dataset grid may be divided intolayers taken at incremental ranges. The layers may take any shape, forexample parallel Cartesian layers or dome shaped layers about apredefined reference point (using spherical coordinates).

A set of equations similar to the two-path attenuation equation isoptionally written for all output grid points within each layer,assuming that the attenuation values for the output grid points in alllayers closer to the reference point, have already been determined. Forthe first layer, the attenuation within the entire previous layer isassumed to be 0 [dB]. This “boundary condition” allows the solution ofthe equations for all layers.

The above described processes results in an estimated map of attenuationcoefficients, which is spatially dependent, and in some cases also timedependent. This map may also be used to correct the map of reflectioncoefficients, inherently produced by reflection-based imaging modes.Combining the two maps, perhaps together with other maps provided by thesystem, can aid in the classification of tissue types. Additionally oralternatively, the complex weights assigned to different transducers 124on transmit and/or on receive may be adjusted for each small scannedvolume based on the attenuation coefficient maps, for example in orderto improve focusing on transmit and/or on receive, thus enhancingspatial resolution.

The above procedures may take into account the spatially dependent gain,for example due to time-gain control (TGC), applied prior to theprocedures by the system hardware and software. For that purpose, alocal TGC correction factor may be added to the attenuation coefficientmap obtained, and/or to the samples used as an input to the process.

In some cases, various additional corrections may be applied to thesampled data and/or the energy measurements prior to the attenuationcorrection process. For example, one may choose to correct for thetwo-way range dependent power decay of the spherical ultrasound wave,which approximately follows the form 1/R⁴ (where R is the distance fromthe transducer). Additionally or alternatively, one can compensate forbeam-shape losses, caused by the fact the energy of the transmit beamand the gain of the receive beam are not homogeneously distributed overall spatial angels, or even over all spatial angles within therespective main-lobes.

The tissue's local attenuation coefficient may depend on the transmittedfrequency. Therefore, when wideband signals are transmitted, the processdescribed above may be applied separately to multiple sub-bands of thereceived signal. The results for the multiple sub-bands may then becombined to obtain the final attenuation coefficient estimation. Thereceived signal may be divided into sub-bands by applying analog and/ordigital filtering to that signal. In some cases, different sub-bands mayalso be sampled separately.

Corrections for Speed of Sound Variability

The average speed of sound in soft tissue is approximately 1540[^(m)/sec]. However, this speed varies between different tissue types.During reflection-based image formation, one often assumes a constantspeed of sound, so that the time delay between signal transmission andthe receipt of the reflected signal is linearly correlated to thedistance from the transducer. Variations in speed of sound introducepositive or negative time delays, making this correlation imprecise.

The actual local speed of sound may be estimated using thetransmission-based UCT mode. This mode can therefore be activated insome sequences with a reflection-based mode, for example interleavingframes, and its output may be used to correct the reflection-based map.

In some embodiments of the invention, local speed of sound measurements,which provide important spatially and/or temporally dependent clinicalinformation and allow improving ultrasound images by applying local timedelay correction, may be performed using only reflection-basedinformation. The following is an explanation of just one method forproviding local attenuation measurements for an ultrasound garment ofthe present invention; as well as existing ultrasound imaging systems.This method is based on the fact that elastic registration betweenmultiple input datasets can provide multiple translation measurement{right arrow over (t)}_(q) (q is the dataset index) for each smalltarget region with respect to a selected reference input dataset. Thesetranslations are indicative of relative time delays. As with signalattenuation, signal time delay is also cumulative along each beam path{right arrow over (r)}_(q). Data acquisition geometry is generallyknown, so that a set of equations may be written, describing therelationships between {right arrow over (t)}_(q) values for differentregions. For example, for a single small target region, viewed by twopaths and {right arrow over (r)}_(q1) {right arrow over (r)}_(q2):

${{\int_{{\overset{->}{r}}_{q\; 1}}\frac{2\; {r}}{c\left( {x,y} \right)}} - {\int_{{\overset{->}{r}}_{q\; 2}}\frac{2{r}}{c\left( {x,y} \right)}}} = {t_{q\; 1} - t_{q\; 2}}$

where c(x,y) is the actual local speed of sound, t_(q1) and t_(q2) arethe scalar time delays along paths {right arrow over (r)}_(q1) and{right arrow over (r)}_(q2) respectively. This equation is referred toas the “two-path time-delay equation”.

A possible geometry used for solving this problem is based on pairs ofopposite collinear reflection beams, which can be provided by thereflection-based beam pairs mode. For each set of beam pairs, one shouldlook for specific patterns, for example maxima or minima. All thelocated patterns in one beam should be located in the other one as well(FIG. 8). The actual location of the peaks, or other patterns, along thebeam pairs axis is denoted by l(x), and the measured locations along thetwo opposite beams are l₁(x) and l₂(x). The local time delay, given inunits of range, is denoted by d(x). Since the overall side-to-side timedelay, D, should be equal in both datasets, it can be easily shown that:

$\begin{matrix}{{l_{1}(x)} = {{l(x)} + {\int_{0}^{x}{{(y)}{y}}}}} \\{{l_{2}(x)} = {{{l(x)} + {\int_{x}^{X}{{(y)}{y}}}} = \left. {{l(x)} + D - {\int_{0}^{x}{{(y)}{y}}}}\Rightarrow{l(x)} \right.}} \\{= {\frac{1}{2}\left\lbrack {{l_{1}(x)} + {l_{2}(x)} - D} \right\rbrack}} \\{{{\int_{0}^{x}{{(y)}{y}}} = {\frac{1}{2}\left\lbrack {{l_{1}(x)} - {l_{2}(x)} + D} \right\rbrack}}}\end{matrix}$

The local speed of sound can be directly extracted from these equations,referred to as the “collinear time-delay equations”, as the time delayis proportional to the difference between the actual speed of sound andthe nominal speed of sound. While these equations may only be precisefor a noise free environment, they should provide acceptable results inreal scenarios as well.

The collinear time-delay equations provide measurements of the localtime delay for the locations of the peaks or other patterns detected.One can assume that the time delay is homogeneously spread over regionsbetween adjacent detected peaks (or other patterns). This computationmay be repeated for multiple beam pairs, thus providing a speed of soundmap for a 2D or 3D region.

This process is only applicable if full side-to-side information hasbeen obtained for all beam pairs. In other cases, one can generate aspeed of sound map for all volumes covered by beam pairs with fullside-to-side coverage, and then use this map to iteratively completemissing information in beams with partial coverage.

In a further embodiment, applicable for example to reflection-basedvolume imaging, the output dataset grid may be divided into layers takenat incremental ranges. The layers may take any shape, for exampleparallel Cartesian layers, or dome shaped layers about a predefinedreference point (using spherical coordinates).

A set of equations is optionally written for all output grid pointswithin each layer, assuming that the speeds of sound for the output gridpoints in all layers closer to the reference point have already beendetermined. For the first layer, the speed of sound in the previouslayer is assumed to be the nominal speed of sound. This “boundarycondition” allows the solution of the equations for all layers.

The resulting spatial map of speeds of sound, which in some cases canalso be time dependent, may be used to correct the reflectioncoefficient map, inherently produced by reflection-based imaging modes.It can also be used separately. Moreover, combining the two maps,perhaps together with other maps provided by the system, can aid in theclassification of tissue types. Additionally or alternatively, thecomplex weights assigned to different transducers 124 on transmit and/oron receive may be adjusted for each small scanned volume based on thespeed of sound maps, for example in order to improve focusing ontransmit and/or on receive, thus enhancing spatial resolution.

The local speed of sound within the tissue may depend on the transmittedfrequency. Therefore, when wideband signals are transmitted, the processdescribed above may be applied separately to multiple sub-bands of thereceived signal. The results for the multiple sub-bands may then becombined to obtain the final speed of sound estimation. The receivedsignal may be divided into sub-bands by applying analog and/or digitalfiltering to that signal. In some cases, different sub-bands may also besampled separately.

Side-lobe Clutter Suppression Techniques

The term “clutter” refers to undesired information that appears in theimaging plane, obstructing the data of interest. One of the most commonreasons for clutter in ultrasound images is effective imaging ofoff-axis objects, lying in a beam's side-lobes. Highly reflectiveregions within these side-lobes, for example surfaces between soft andhard tissues, may produce significant contributions to the measuredsignal.

An iterative process may be devised to minimize clutter effects:

-   -   1) Acquire one or more frames of data for the target volume,        using, for example, an ultrasound garment 110-based system.    -   2) For each sample (range gate) at each beam position:        -   i) Calculate the beam pattern for the current range, with            respect to the applicable scanning apex, at all other beam            positions, normalized so that the peak value would be 1.0.        -   ii) For complex measurements—subtract from the sample the            value at the same range, with respect to the applicable            scanning apex, for all other beam positions, multiplying            each value by the relevant normalized beam pattern value.            Alternatively, only beam positions for which the measurement            and/or the normalized beam pattern value is high are used.            The criterion for selecting the beam positions used for a            certain range gate may be, for example, that the measurement            and/or the normalized beam pattern value and/or their            multiplication result exceeds a certain threshold or belongs            to the group of B highest values, where B is a constant. The            second method is also applicable to real measurements.        -   iii) Repeat step ii until certain cessation criteria have            been met. This is required because all measurements are            affected by reflectors in all beam positions, so that there            are interdependencies between the samples. The cessation            criteria may be as simple as reaching a certain number of            iterations. More complicated criteria may refer to the            average magnitude of changes made in the last iteration, or            the relative average magnitude of changes in the last            several iterations.

This procedure assumes that the effects of attenuation and variations inthe speed of sound are not severe, so that data from different beampositions can be compared. This issue can be avoided by applyingattenuation correction techniques and/or time delay corrections prior toclutter suppression.

This process requires that for each processed beam, taken at a spatialangle (θ,φ), information would be available for θ±Δθ and φ±Δφ, where Δθand Δφ are high, for example, higher than 30°, or even very high, forexample higher than 45°.

The inventor has discovered that some embodiments of present ultrasoundprobes cannot provide such an angular coverage, but that such angularcoverage may possibly be achieved in ultrasound garment 110-basedsystems. Data acquired by more than one sub-array may result indifferent attenuation models for different sub-arrays. The effect ofthese differences may be mitigated by applying attenuation correctionschemes, such as those described hereinabove.

Computer Aided Diagnosis Techniques

Diverse computer aided diagnostic tools may be developed in order tostreamline the diagnostic process and make it quantitative rather thanqualitative. Some clinical applications may also require organ specifictools. For instance, a software tool may be developed whichautomatically detects the fetal skin surface, delineating it from theamniotic fluid. Based on this surface, various standard imaging views,for example the sagittal or coronal view of the brain, may beautomatically defined by the software and displayed to the operator.Another example is a tool designed for evaluating fissure complexitywithin the fetal brain.

Additional System Modes Doppler Mode

The Doppler effect is the most common tool for measuring blood flowvelocities and tissue motion velocities in standard ultrasound imagingsystems. For reflection-based ultrasonic imaging, this effect isdescribed by the following equation:

$f_{D} = \frac{2f\; v\; {\cos (\theta)}}{c}$

where f is the transmitted frequency; v is the absolute flow (or motion)velocity; θ is the angle between the effective directions of theultrasonic beam and the flow (or motion) velocity; c is the wave speed;and f_(D) is the Doppler shift, i.e., the difference between thefrequencies of the observed and the transmitted ultrasound. v cos(θ) isthe radial velocity component, i.e., the velocity's component along theline of sight from the transducer's phase center to the target, so thatthe Doppler shift is directly proportional to the radial velocity.

Five types of Doppler modes are usually supported by ultrasound systems:

-   -   i. CW Doppler studies, which provide the overall radial velocity        spectrum for a specific beam direction. The output usually takes        the form of a two-dimensional graph, where the horizontal axis        is the time index and the vertical axis is the radial velocity,        which may either be positive or negative. The gray-level of each        pixel denotes the local ratio, along a selected direction,        between the number of particles moving at the relevant radial        velocity and the total number of particles. Thus, the outlines        of the graph show the maximal velocity as a function of time.    -   ii. PW Doppler studies, which provide the radial velocity        spectrum for a selected depth along a specific angular        direction, as a function of time. The display method is        identical to that used in CW Doppler studies.    -   iii. Color flow Doppler imaging, which uses PW, superimposes a        color representation of the dominant radial blood flow velocity        (for each pixel) over a 2D or 3D ultrasonic image, which may or        may not be time dependent.    -   iv. Tissue Doppler imaging can assess the radial tissue motion        velocity in vascular and cardiac imaging using PW. As in color        flow Doppler imaging, the information is superimposed over the        ultrasonic image.    -   v. Power Doppler imaging, which is similar to color flow Doppler        and tissue Doppler imaging. It displays for each pixel the        signal energy for the local dominant Doppler shift. The signal        energy is proportional to the number of particles within the        pixel volume which move at the dominant radial velocity.

Both CW Doppler studies and PW Doppler studies may be used to measureeither blood flow velocity, for example through a valve or a bloodvessel, or muscle/valve motion velocity, whose peaks are normally atmuch lower velocities.

All the above Doppler modes can be supported by an ultrasound garment110-based system. Additional benefits may also be obtained by the use ofmultiple sub-arrays. Some applications:

-   -   i. In PW Doppler studies, a full spectrum for a specific region        may be acquired from multiple directions, thus extending the        information provided to the clinician.    -   ii. In CW Doppler studies, which provide range independent        information for a specific direction, one may use two or more        intersecting beams, whose boresight directions may either be        constant or changing over time, to extract spatially dependent        data. For example, two beams may be used, the first pointing in        a specific direction, whereas the second one scans the path of        the first beam. If an exceptionally low or an exceptionally high        value is found along the first beam, and is found again, not        necessarily with the same value, for a specific direction of the        second beam, one can assume that the extreme value corresponds        to the intersection point between the first and second beam.    -   iii. In color flow Doppler and tissue Doppler imaging, one can        scan a certain volume using two or more sub-arrays, either on        receive only, or both on transmit and on receive. Two or more        points of view may be used to reconstruct for each pixel a 2D        projection of the 3D velocity vector corresponding to the        dominant velocity. Three or more points of view may be used to        reconstruct the full 3D velocity vector for each pixel. This can        be performed as follows: The radial velocity measurement for the        i'th point of view, v_(i) ^(r), as made using a beam whose        boresight unit vector is {circumflex over        (b)}_(i)=(x_(i),y_(i),z_(i)), provides the projection of the        local dominant velocity vector {right arrow over        (v)}=(v_(x),v_(y),v_(z)) on {circumflex over (b)}_(i), i.e.,        {circumflex over (b)}_(i)·{right arrow over (v)}. All unit        vectors {circumflex over (b)}_(i) are known, so that the vector        {right arrow over (v)} may be deduced from three measurements:

$\begin{pmatrix}v_{1}^{r} \\v_{2}^{r} \\v_{3}^{r}\end{pmatrix} = {\left. {\begin{pmatrix}x_{1} & y_{1} & z_{1} \\x_{2} & y_{2} & z_{2} \\x_{3} & y_{3} & z_{3}\end{pmatrix}\begin{pmatrix}v_{x} \\v_{y} \\v_{z}\end{pmatrix}}\Rightarrow\begin{pmatrix}v_{x} \\v_{y} \\v_{z}\end{pmatrix} \right. = {\begin{pmatrix}x_{1} & y_{1} & z_{1} \\x_{2} & y_{2} & z_{2} \\x_{3} & y_{3} & z_{3}\end{pmatrix}^{- 1}\begin{pmatrix}v_{1}^{r} \\v_{2}^{r} \\v_{3}^{r}\end{pmatrix}}}$

-   -   where −1 denotes a matrix inversion operator. A similar process        can be applied to obtain only a 2D projection of the vector.    -   Using more points of view than needed allows obtaining a vector        estimate for each group of two or three points of view.        Averaging over the results may provide more accurate results.

In some cases, one can limit the volume scanned for Doppler processingto a specific region, which is either operator defined or automaticallyselected. The specific region can be defined based on anatomic maps, forexample by locating blood vessels of interest and their immediatesurroundings. By limiting the scanned volume, the number of beampositions required to scan the volume is decreased, so that the overallrefresh rate can be increased. This is important when significantchanges are expected over time, for example in cardiac imaging.

Moving-Organ Tissue Tracking

Some organs, for example blood vessels, the cardiac muscle, and thegastrointestinal system, move over time. One can evaluate this motion inultrasound imaging by tracking small localized regions of the imagebetween consecutive image frames; for example as described byLedesma-Carbayo M J, Kybic J, Desco M, et al.; “Spatio-Temporal NonrigidRegistration for Ultrasound Cardiac Motion Estimation”; IEEETransactions on Medical Imaging 2005; 24:1113-1126. This can be done byapplying various elastic registration techniques, for example by opticflow methods, to datasets obtained at subsequent time frames.

Such schemes may be utilized by ultrasound garment 110-based systems.For example, they may be applied to datasets obtained by one or moresub-arrays and/or to compounded datasets, produced by any imaging mode.The resulting information can be provided to the operator.

Contrast Imaging

Several contrast ultrasound imaging methods are known in the art. Insome cases, these methods are tailored to a specific organ. All thesemethods are also applicable to ultrasound garment 110-based systems.

Elastography

In some embodiments, ultrasound garment 110-based systems may provideelastography features. Any type of internal or external mechanicalstimulus, generated by any source, may be used for that purpose. Forexample, a stimulus may be generated by one or more loudspeakers, one ormore transducers 124, and/or one or more apparatuses comprising ahousing with a movable surface, as taught in US Patent Application2002/0068870; Jun. 6, 2002 by Alam S K, Feleppa E J, King M, Lizzi F L;“Hand Held Mechanical Compression Device for Inducing Tissue Strain”.

The vibration frequency of the source optionally will vary between 1[Hz] and 100 [kHz].

The inventor has discovered that the use of multiple sources may allowproducing more localized excitation by means of interference, as well asimproving the control over the directionality of the mechanical impulsegenerated.

Another method for creating a mechanical stimulus, is applying aconstant or time-variable force to the subject's skin surface, or to aninternal organ, during invasive procedures. While a mechanical force isbeing applied, either in a cyclic fashion (vibration) or in a non-cyclicfashion, tissue tracking techniques, for example as described by in the“Moving Organ Tissue Tracking” subsection, may be applied, producingestimates of the local tissue motion vectors in response to themechanical force. Additionally or alternatively, Doppler-based imagingmodes, as described herein, may be used to estimate the localtime-dependent motion vectors of the tissue. These vectors areindicative of the tissues' mechanical properties, and may be used fortissue classification purposes, for example detection of malignant orbenign tumors.

In a possible configuration, one or more low-frequency sound sources(LFSSs), such as loudspeakers, are placed either in direct contact with,or in close proximity to, the subject's skin surface. These LFSSs, whichcan be integrated with an ultrasound garment 110-based system or placednear it, produce directional oscillations within the imaging targetvolume. In this configuration, the LFSS carrier frequency shouldoptionally be lower, by a factor of at least 5, than the highest pulserepetition frequency used by any sub-array of ultrasound garment 110system during the elastography mode. This can aid in preventing smearingof the measured signal, for example, so as to assure that local tissuemotion during the pulse is insignificant.

The LFSS carrier frequency is typically selected to be low enough toproduce negligible tissue motion during the acquisition of a fullimaging frame, or at least a large sector of such a frame, so thatimages can be obtained at multiple phases of a single LFSS oscillation.If that is not the case, the temporal sampling for each small tissueregion is unsynchronized with the LFSS oscillation, so that one may onlybe able to estimate the span or extent of the local tissue motion overmultiple cycles rather than determine the time dependent motion pattern.

Photoacoustic and Thermoacoustic Imaging

Photoacoustic imaging is a medical imaging modality based on thephotoacoustic effect. Non-ionizing laser pulses are delivered intobiological tissues; some of the delivered energy is converted into heat,leading to transient thermoelastic expansion and thus ultrasonicemission. The generated ultrasonic waves are then detected by ultrasonictransducers to form images. The energy of the ultrasonic emission isindicative of the local energy deposition, and therefore providesinformation regarding the local optical absorption. The energy of theultrasonic signals received by the ultrasonic transducers is alsoaffected by two types of artifacts:

-   -   i. Electromagnetic phenomena, occurring along the path of the        electromagnetic signal.    -   ii. Ultrasonic phenomena, occurring along the ultrasound        propagation path.        These phenomena include, for example, absorption, reflection,        and scattering.

An exemplary photoacoustic imaging system is described by Zhang H F etal.; “Functional Photoacoustic Microscopy for High-Resolution andNoninvasive In-vivo Imaging”; Nature Biotechnology 2006; 24:848-851.

When radio-frequency (RF) pulses are used, the technology is referred toas thermoacoustic imaging rather than photoacoustic imaging.

Optical absorption and RF absorption are closely associated withphysiological properties. For instance, optical absorption is known tobe related to local hemoglobin concentration and oxygen saturation.Another exemplary application is visualization of blood vessels, whichis based on the fact that both optical absorption and RF absorption ofblood tend to be high compared to most other tissue types. Generallyspeaking, the frequency of the light and/or RF waves used may affect thephysiologic properties observed by photoacoustic or thermoacousticimaging systems, as well as their maximal penetration depth, which tendsto increase as the frequency decreases.

The inventor has discovered that ultrasound garments may haveapplication in photoacoustic and thermoacoustic imaging. The followingdescription presents just some of the many possible means of extractinginformation to provide photoacoustic and thermoacoustic imaging data.

In some embodiments, referring back to FIG. 1, one or more sources oflight or RF radiation (jointly referred to hereinbelow aselectromagnetic radiation) may be incorporated into ultrasound garment110-based systems or placed in close proximity to them. The sources oflight may include, for example, laser relayed by optic fibers. Lensesmay optionally be used to increase the laser beams' coverage area. TheRF sources may include any type of RF-fed antenna known in the art,which fits the required transmission power and frequency band, forexample, dipole antennas, horn antennas, planar-array antennas, and/orphased-array antennas.

The electromagnetic radiation sources may transmit any waveform,including CW and PW. Optionally, amplitude modulation and/or frequencymodulation may be utilized, as well as coded excitation techniques suchas binary sequences and poly-phase codes. Different electromagneticradiation sources may also use different waveforms, thus allowingsimultaneous utilization of several electromagnetic radiation sources.

In embodiments, the ultrasound transducers 124 and beam-forming unit 120should optionally be configured to generate one or more concurrentreceive beams, whose spatial directions may be constant ortime-dependent. The timing of these receive beams may be synchronized toelectromagnetic pulse transmission. Since the speed of sound in tissuesis lower than the speed of light by several orders of magnitude, thetime delay between electromagnetic pulse transmission and ultrasonicsignal reception should be approximately proportional to the distancebetween the tissue from which ultrasound waves emanate and thetransducers. Additionally or alternatively, the directions of thereceive beams may be adjusted to match the coverage volume of theelectromagnetic radiation sources.

Numerous receive beam scanning configurations may be considered. Forexample, one of more sub-arrays may be defined, each of which scanning aplane or a volume. Additionally or alternatively, a plurality of receivebeams may be defined, some of which are parallel and/or directed at acertain point in space. Another option is using pairs of oppositecollinear beams.

Processing unit 122 may then apply any reconstruction algorithm known inthe art or described herein. In embodiments, reflection mode and/ortransmission mode UCT algorithms may be applied, with or without thegeometry emulation algorithm. Additionally or alternatively, attenuationcorrection techniques and/or corrections for speed of sound variability,as described hereinabove, may be utilized in order to minimize theeffect of ultrasonic artifacts on local electromagnetic absorptionestimates. The calculations may take into account the one-way ratherthan two-way nature of the ultrasonic artifacts in these cases.

In embodiments, further techniques may be applied to reduce the effectof electromagnetic artifacts occurring between the electromagneticsource and the tissue emitting ultrasound waves. For example, arange-dependent correction factor may be applied. The correction factormay also take into account the ultrasonic signal as measured for tissuesalong the path between the electromagnetic source and the tissueemitting ultrasound waves.

In further embodiments, additional information may be obtained bytransmitting more than one type of electromagnetic waveform, for examplemore than one transmission frequency.

Additionally or alternatively, where multiple electromagnetic radiationsources are used, the ultrasonic data collected using differentelectromagnetic radiation sources may be compared and analyzed. Forexample, when comparing the ultrasonic data along a line connecting twoelectromagnetic radiation sources, as collected by the two said sources,the collinear time-delay equations may be applied to estimate andoptionally correct the electromagnetic time delays within the tissues.

Therapeutic Systems High Intensity Focused Ultrasound

As described hereinabove, HIFU is an ultrasound-based therapeutictechnique. In some embodiments, ultrasound garment 110-based systems canbe used as a source of imaging information, guiding an HIFU apparatus.In certain embodiments, this imaging information may also include localtemperature estimation at the target region, for controlling HIFUoperation. Local temperature may be evaluated based on the multipleparameters measured for each point in space as a function of time, forexample local reflection coefficient, local attenuation coefficient, andlocal speed of sound. In further embodiments, an array of high intensitytransducers 124 may be integrated with or into ultrasound garment 110.The radiating transducer components used for HIFU may either bededicated to HIFU operation or be used for imaging purposes as well.

The inventor has discovered that the local measurements of ultrasoundattenuation and/or local speed of sound, made by the processes providedherein, can be used to adaptively optimize the beam forming parametersof the high intensity transducer components. As a result, the focalpoint can be smaller and more precisely defined, allowing better controlover the target region. Additionally or alternatively, lower transmittedpower levels may be used to obtain the same effect at the target region,thus improving the system's safety level.

It is expected that during the life of a patent maturing from thisapplication many relevant ultrasound garments will be developed, and thescope of the term ultrasound garment is intended to include all such newtechnologies a priori.

As used herein the term “about” refers to ±25%.

The terms “comprises”, “comprising”, “includes”, “including”, “having”and their conjugates mean “including but not limited to”.

The term “consisting of” means “including and limited to”.

The term “consisting essentially of” means that the composition, methodor structure may include additional ingredients, steps and/or parts, butonly if the additional ingredients, steps and/or parts do not materiallyalter the basic and novel characteristics of the claimed composition,method or structure.

As used herein, the singular form “a”, “an” and “the” include pluralreferences unless the context clearly dictates otherwise. For example,the term “a compound” or “at least one compound” may include a pluralityof compounds, including mixtures thereof.

Throughout this application, various embodiments of this invention maybe presented in a range format. It should be understood that thedescription in range format is merely for convenience and brevity andshould not be construed as an inflexible limitation on the scope of theinvention. Accordingly, the description of a range should be consideredto have specifically disclosed all the possible subranges as well asindividual numerical values within that range. For example, descriptionof a range such as from 1 to 6 should be considered to have specificallydisclosed subranges such as from 1 to 3, from 1 to 4, from 1 to 5, from2 to 4, from 2 to 6, from 3 to 6, etc., as well as individual numberswithin that range, for example, 1, 2, 3, 4, 5, and 6. This appliesregardless of the breadth of the range.

Whenever a numerical range is indicated herein, it is meant to includeany cited numeral (fractional or integral) within the indicated range.The phrases “ranging/ranges between” a first indicate number and asecond indicate number and “ranging/ranges from” a first indicate number“to” a second indicate number are used herein interchangeably and aremeant to include the first and second indicated numbers and all thefractional and integral numerals therebetween.

As used herein the term “method” refers to manners, means, techniquesand procedures for accomplishing a given task including, but not limitedto, those manners, means, techniques and procedures either known to, orreadily developed from known manners, means, techniques, and proceduresby practitioners of the mathematical, physical, chemical,pharmacological, biological, medical, computer sciences, electricalengineering, mechanical engineering, and biomedical engineering arts.

As used herein, the term “treating” includes abrogating, substantiallyinhibiting, slowing or reversing the progression of a condition,substantially ameliorating clinical or aesthetical symptoms of acondition or substantially preventing the appearance of clinical oraesthetical symptoms of a condition.

It is appreciated that certain features of the invention, which are, forclarity, described in the context of separate embodiments, may also beprovided in combination in a single embodiment. Conversely, variousfeatures of the invention, which are, for brevity, described in thecontext of a single embodiment, may also be provided separately or inany suitable subcombination, or as suitable in any other describedembodiment of the invention. Certain features described in the contextof various embodiments are not to be considered essential features ofthose embodiments, unless the embodiment is inoperative without thosecomponents.

In embodiments, some of the algorithms presented herein, such as thegeometry emulation algorithm, and/or their combinations orsub-combinations, may be utilized on ultrasound garment embodiments aswell as, in some instances, on existing technology.

Ultrasound garment technology may provide some advantages over knownimaging modalities. Partial comparative analysis between certaindisclosed ultrasound garment configurations and known ultrasound, MRIand CT systems is provided in the following Appendix A; which togetherwith the above descriptions illustrate some embodiments of the inventionin a non-limiting fashion.

APPENDIX A The inventor has discovered the following possible analyticalaspects of ultrasound garment systems and presently availableultrasound, MRI and CT systems. (“fps” stands for “frames per second”.)US Garment Systems Ultrasound MRI CT General Clinical Aspects ScannedVolume May provide a large 2D plane or small Large 3D volume 3D volume3D volume Clinical Data Possibly any plane Limited by possible Any planeor volume within the Accessibility or volume within transducer large 3Dvolume the large 3D locations and tilts volume Refresh Rate May be highfor High (~20 fps) for Low (or still) for large 3D volumes large 3Dvolumes 3D volumes General Image Expected to be high Relatively low HighQuality Inter- and Intra- Expected to be low High Low ObserverVariability Tissue Classification Generally Not supported Not supportedsupported Imaging for Generally Not supported Not supported Continuoussupported Monitoring Exam Location May be bedside Special exam roomSafety No ionizing radiation No ionizing Ionizing radiation radiationContrast agents often used Clinical Aspects Specific to Obstetrics andGynecology Invasive/Non- May be non- Trans-abdominal Non-invasiveinvasive invasive transducers: non-invasive Trans-vaginal transducers:invasive, limited imaging views Additional Clinical Aspects ImageQuality Generally minimal High Minimal Dependence on HardwareConfiguration Cine-loop Acquisition May take Several seconds Severalminutes Duration Blood Flow Velocity 3D flow vectors Radial componentCoarse flow Not measurable Measurement generally may be of flow vectorsvelocity measured measured measurements

Although the invention has been described in conjunction with specificembodiments thereof, it is evident that many alternatives,modifications, and variations will be apparent to those skilled in theart. Accordingly, it is intended to embrace all such alternatives,modifications, and variations that fall within the spirit and broadscope of the appended claims.

All publications, patents, and patent applications mentioned in thisspecification are herein incorporated in their entirety by referenceinto the specification, to the same extent as if each individualpublication, patent, or patent application was specifically andindividually indicated to be incorporated herein by reference. Inaddition, citation or identification of any reference in thisapplication shall not be construed as an admission that such referenceis available as prior art to the present invention. To the extent thatsection headings are used, they should not be construed as necessarilylimiting.

1-81. (canceled)
 82. An ultrasound assembly, comprising: i. a garmentconfigured to be affixed to a portion of a living body; ii. at least oneultrasound transducer having a fixed position on said garment andconfigured to provide at least one of: a) produce; and b) receiveultrasound signals that pass through the living body; iii. an ultrasoundprocessing unit operatively associated with said at least one ultrasoundtransducer and configured to process said ultrasound signals followingpassage through the living body; and iv. an ultrasoundoperator-interface unit operatively associated with said ultrasoundprocessing unit and configured to provide information with respect tosaid ultrasound signals following passage through the living body,wherein said at least one transducer comprises at least one transducerarray.
 83. The assembly according to claim 82, including an ultrasoundbeam-forming unit configured to produce ultrasound beam propagationwherein at least one of: i. at least one sub-array; ii. said at leastone array; iii. a plurality of transducer arrays; and iv. said at leastone transducer are configured to provide beams consisting of at leastone of: a. transmitting; and b. receiving, and said ultrasoundprocessing unit includes a software module configured to processinformation from said provided beams.
 84. The assembly according toclaim 82, including at least one rail juxtaposed along said garment andat least one of: i. at least one sub-array; ii. said at least one array;iii. a plurality of transducer arrays; and iv. said at least onetransducer, are configured to move along said at least one rail.
 85. Theassembly according to claim 82, including at least onetransducer-locating sensor operatively associated with said ultrasoundprocessing unit, said at least one transducer-locating sensor occupyingat least one position of: i. on said garment; and ii. at a distance fromsaid garment, and said ultrasound processing unit includes a softwaremodule configured to process spatial information from said at least onetransducer-locating sensor.
 86. The assembly according to claim 83,wherein said system includes at least one of: i. a plurality ofsub-arrays; and ii. said plurality of transducer arrays, and whereinsaid ultrasound processing unit includes a software module configured tocompound signals received to produce at least one output dataset. 87.The assembly according to claim 86, wherein said at least one datasetcomprises at least two datasets which are combined, thereby achieving atleast one of: i. extending a field of view; ii. reducing speckle noise;iii. improving signal-to-noise ratio; iii. reducing shadowing artifacts;iv. reducing clutter artifacts; v. enhancing spatial resolution; and vi.enhancing image contrast.
 88. The assembly according to claim 83,wherein said ultrasound processing unit includes a software-basedcompounding module configured to produce output datasets from inputdatasets; wherein said input datasets comprise information from saidprovided beams; by: i. interpolating data for each input dataset to acoordinate grid of every output dataset; ii. calculating a weighted meanover all input datasets per output grid point, using input datasetswhose field of view covers the relevant grid point.
 89. The assemblyaccording to claim 88, wherein the weights for said weighted mean may becomputed according to various criteria, said various criteria comprisingat least one of: i. higher weights are assigned to input datasets whosenearby pixels provide better lateral resolution; ii. weights areassigned in inverse proportion to the effective volume of the relevantpixels within an input dataset; iii. weights are assigned according to asignal-to-noise ratio estimate per input dataset; and iv. low weightsare assigned to datasets in which the local signal level issignificantly lower than in the other datasets.
 90. The assemblyaccording to claim 83, including at least one transducer, producingdifferent waveforms, wherein said ultrasound processing unit includes asoftware module-based process configured to provide various functions ofdatasets acquired by said at least one transducer at different waveformsthat are calculated, thereby providing information with respect to localtissue type.
 91. The assembly according to claim 83, wherein saidultrasound processing unit is configured to receive input datasetsacquired from multiple directions, and, for at least one small targetregion located in more than one of said input datasets, apply an elasticregistration process to relevant measurements in said input datasets.92. The assembly according to claim 91, wherein said ultrasoundprocessing unit extracts from outputs of said elastic registrationprocess at least one of: i. local attenuation coefficient measurements;wherein said elastic registration process is applied to at least two ofsaid input datasets undergoing cumulative attenuation along differentpaths; wherein said cumulative attenuation results from localattenuation within said living body; and ii. local speed of soundmeasurements; wherein said elastic registration process is applied to atleast two of said input datasets undergoing cumulative time delays alongdifferent paths; wherein said cumulative time delays result from localattenuation within said living body.
 93. The assembly according to claim83, wherein said ultrasound processing unit includes a softwaremodule-based process configured to reduce clutter effects, comprising:i. acquiring at least one frame of data for the target volume; and ii.for each sample range-gate at each beam position calculating a beampattern for the current range, with respect to an applicable scanningapex, at all other beam positions; wherein said beam pattern isnormalized so that the peak value is 1.0.
 94. The assembly according toclaim 93, wherein said software module-based process is furtherconfigured to subtract from said sample range-gate measurement values atthe same range, with respect to said applicable scanning apex, for agroup of other beam positions, where each measurement value ismultiplied by the corresponding said beam pattern value, and whereinsaid group of other beam positions comprises beam positions for which atleast one value is high, said high value comprising at least one of: i.a measurement; and ii. said beam pattern.
 95. The assembly according toclaim 83, wherein said ultrasound processing unit includes a softwaremodule configured to generate ultrasound computed tomography orultrasound diffraction tomography images by geometrically transformingat least one of: i. scanning processing parameters; and ii. signalprocessing parameters; to obtain samples equivalent to those obtainedusing at least one of: a. cylindrical geometry; and b. sphericalgeometry.
 96. The assembly according to claim 82, including at least oneelectromagnetic radiation source, said at least one electromagneticradiation source occupying at least one position of: i. on said garment;and ii. at a distance from said garment, and said at least oneelectromagnetic radiation source includes at least one of: a. lightsource; and b. radio-frequency (RF) source, wherein said ultrasoundprocessing unit includes a software module-based process configured toextract from ultrasonic reflections information regarding at least oneof: i. local optical absorption; and ii. local RF absorption.
 97. Theassembly according to claim 96, wherein said ultrasound processing unitincludes a software module-based process configured to perform at leastone of the following techniques: i. ultrasound computed tomography; ii.ultrasound computed tomography with geometric transformation; iii.attenuation correction using local attenuation coefficient measurements;and iv. time-delay correction using local speed of sound measurements.98. The assembly according to claim 83, wherein said ultrasoundbeam-forming unit is configured to support at least one imaging modecomprising at least one of: i. reflection-based volume imaging; ii.reflection-based ultrasound computed tomography (UCT); iii.reflection-based ultrasound diffraction tomography (UDT); iv.reflection-based beam pairs; v. transmission-based UCT; and vi.transmission-based UDT.
 99. The assembly according to claim 83, whereinsaid ultrasound processing unit includes a software module-based processconfigured to receive data from calibration beams, wherein saidcalibration beams include at least one of: i. transmit beams; and ii.receive beams, and said process aligns said transmit beams and saidreceive beams.
 100. The assembly according to claim 83, wherein multiplestrong reflectors are embedded in known positions along said garment;said strong reflectors comprising at least one of: i. different shapes;and ii. different reflection characteristics, and said ultrasoundprocessing unit includes a software module configured to discriminatebetween said strong reflectors.
 101. The assembly according to claim 83,wherein an array of high intensity transducers is integrated into saidultrasound garment and at least one said high intensity transducer is atleast one of: i. dedicated to high intensity focused ultrasound (HIFU)operation; and ii. dedicated to imaging purposes, and wherein saidultrasound processing unit includes a software module configured toutilize at least one of: i. the local measurements of ultrasoundattenuation; and ii. the local measurements of speed of sound, toadaptively optimize the beam-forming parameters of said high intensitytransducers.
 102. The assembly according to claim 82, wherein saidgarment comprises at least one apparel comprising at least one of: abelt; a shirt; and a pair of pants.